Spread spectrum communication device and spread spectrum communication method

ABSTRACT

In a compressed mode, a spread spectrum communication device interleaves bit units across multiple frames using an interleaver, reduces the spreading factor using a framing/spreading unit, outputs the compressed mode frames at a predetermined compressed mode frame timing, and increases the average transmission power in the compressed mode at a radio frequency transmitter. Furthermore, a handover between different frequencies is carried out by establishing synchronization to another frequency carrier, based on a first search code and a second search code which have been detected, and moreover, a handover between different communication systems is carried out by establishing synchronization to a GSM, based on an FCCH and a SCH which have been detected.

TECHNICAL FIELD

This invention relates to a communication device applied in a codedivision multiple access (CDMA) communication system and a methodthereof. More particularly this invention relates to a spread spectrumcommunication device for improving interleave transmission andtransmission power control in spread spectrum communication, and forrealizing handovers between different frequencies and a method thereof.

BACKGROUND ART

In a CDMA cellular system, because the same carrier frequency is usedrepeatedly in every cell there is no need for handovers betweenfrequencies within the same system. However, considering a case such aswhen existing systems are present together, there is a need forhandovers between different carrier frequencies. Three points pertainingto detailed cases are described below.

As a first point, in a cell where there is considerable traffic, aseparate carrier frequency is used to accommodate the increased numberof subscribers, and a handover may be performed between those cells. Asa second point, when an umbrella cell constitution is used, differentfrequencies are allocated to large and small cells, and handovers areperformed between the cells. Then, as a third point, there are cases ofhandovers between a third generation system, such as a W(Wideband)-CDMAsystem, and a second generation system, such as a current mobiletelephone system.

When performing handovers in cases such as those mentioned above, it isnecessary to detect the power of carriers at the different frequencies.To achieve this detection, the receiver needs to only have a structurecapable of detecting two frequencies. However, this increases the sizeof the constitution of the receiver, or makes the constitutioncomplicated.

Furthermore, two types of handover method may be considered: a mobileassisted handover (MAHO) and a network assisted handover (NAHO).Comparing the MAHO and NAHO methods, NAHO reduces the burden of themobile device, but to be successful, it should be necessary tosynchronize the mobile device and the base station, whereby theconstitution of the base station and the network becomes complicated andlarge in order to be capable of tracking each individual mobile device.

For such reasons, the realization of the MAHO method is more desirable,but to determine whether or not to handover, it is necessary to measurethe strength of carriers of different frequencies at the mobile devices.However, a CDMA cellular system differs from a time division multiplexaccess (TDMA) system used in a second generation, in that it usesordinarily continuous transmission for both transmission/reception. Inthis continuous transmission/reception technique, unless receiverscorresponding to two frequencies are prepared, it is necessary to stopthe timing of the transmission or the reception and measure the otherfrequency.

There has been disclosed a technique relating to a compressed modemethod, for time-compressing the transmission data in the usual mode andtransmitting it in a short time, thereby creating some spare time whichcan be utilized to measure the other frequency carrier. As an example ofthis, there is Japan Patent Application National Publication (Laid-Open)(JP-A) No. 8-500475 “Non-continuous Transmission for Seamless Handoversin DS-CDMA Systems”. This application discloses a method of realizing acompressed mode, wherein the spreading factor of the spreading code usedis lowered to compress the transmission duration.

The method of realizing the compressed mode according to the aboveapplication will be explained below. FIG. 36 shows an example oftransmissions in a normal mode and a compressed mode in a conventionalCDMA system. In FIG. 36, the vertical axis represents transmissionrate/transmission power, and the horizontal axis represents time. In theexample of FIG. 36, the compressed mode transmission is inserted betweennormal transmission frames.

In the transmission in the compressed mode, a non-transmission timing isprovided in the downlink frame, and can be set to a desired period oftime (duration). This non-transmission timing represents idle periodduring which the strength of the other frequency carrier is measured. Inthis way, slotted transmission can be achieved by inserting the idleperiod during transmission of compressed mode frames.

In this type of compressed mode transmission, transmission powerincreases in accordance with the time ratio between the idle period andthe frame (compressed mode frame) transmission timing, and therefore, asshown in FIG. 36, the compressed mode frame is transmitted at a highertransmission power than the frame in normal transmission. As aconsequence, transmission quality can be maintained even in frametransmission in compressed mode.

In addition to the application mentioned above, as an example ofpertinent literature there is Gustafsson, M. et al: “Compressed ModeTechniques for Inter-Frequency Measurements in a Wide-band DS-CDMASystem”, Proc. of 8th IEEE PIMRC '97. This research paper disclosestechniques for realizing compressed mode in cases other than when thespreading factor is lowered, namely when the coding rate is increased,when multi-code transmission is used, and when a multi-bit transmissionmodulation system such as 16QAM is used.

However, in conventional examples such as the application mentionedabove, since transmissions are interleaved in units of one frame andwithin one frame, the interleaving time for slotted transmission (in thecompressed mode) is more compressed than in normal transmission.Consequently, the interleaving size is shortened which leads to aproblem of poor decoding at the reception side.

Furthermore, in conventional examples such as the literature mentionedabove, since the length of interleaving time is shortened when usingcompressed mode transmission, there is increased deterioration of signalquality with respect to fading, and, since no TPC (transmission powercontrol) command bit is sent during non-transmission, it is not possibleto achieve high-speed TPC, leaving a subsequent problem of poor signalquality.

Furthermore, in conventional examples such as the application andliterature mentioned above, the spreading factor is lowered whencarrying out a compressed mode transmission. However, in general,lowering of the spreading factor indicates that a spreading code havinga short code-length is being used. However, since the number ofspreading codes that can be used is directly proportional to the squareof the code-length, there is a problem that there are extremely fewspreading codes having short code-lengths, and these spreading coderesources, which are vital for realizing compressed mode transmission,are consumed.

It is an object of the present invention to solve the problems describedabove by providing a spread spectrum communication device and a spreadspectrum communication method capable of preventing deterioration insignal quality caused by compressed mode, with respect to interleaving,transmission power control, spreading code allocation methods and thelike to minimize the effects of transmission errors.

DISCLOSURE OF THE INVENTION

A spread spectrum communication device according to an aspect of thepresent invention is applied in a code division multiple access systemfor continuously transmitting frames in a normal mode, andintermittently transmitting compressed frames in a compressed mode, andis characterized in that it comprises an interleaving unit forinterleaving in bit units a frame or a compressed frame, which is a unitof a transmission data stream, to minimize effects of transmissionerrors; a compressing/intermittent transmitting unit for compressing aframe prior to or after interleaving in the compressed mode, andmoreover, intermittently outputting the compressed frame to theinterleaving unit if the compressed frame has not yet been interleaved,and intermittently outputting the compressed frame to a device on areception side if the compressed frame has been interleaved; a controlunit for controlling the operation of interleaving in bit units of theinterleaving unit, and the compressing/intermittent transmittingoperation of the compressing/intermittent transmitting unit; the controlunit controlling the interleaving unit to perform interleaving in bitunits across multiple frames in the compressed mode.

According to this invention, in the compressed mode, multiple frames areinterleaved in bit units to minimize effects of transmission errors,whereby it is possible to secure appropriate interleaving time in thecompressed mode in the same way as in the normal mode, and consequently,poor performance caused by interleaving in bit units can be prevented.

A spread spectrum communication device according to a next aspect of theinvention is characterized in that the interleaving unit has a memorysize in correspondence with the number of frames to be interleaved inthe compressed mode.

According to this invention, since the memory size used is incorrespondence with the number of frames to be interleaved in thecompressed mode, interleaving in bit units can be performed in a numberof frames sufficient to minimize the effects of transmission errors inthe compressed mode.

A spread spectrum communication device according to a next aspect of theinvention is applied in a code division multiple access system forcontinuously transmitting frames in a normal mode, and intermittentlytransmitting compressed frames in a compressed mode, and characterizedin that it comprises an interleaving unit for interleaving in bit unitsa frame or a compressed frame, which is a unit of a transmission datastream, to minimize effects of transmission errors; acompressing/intermittent transmitting unit for compressing a frame priorto or after interleaving in the compressed mode, and moreover,intermittently outputting the compressed frame to the interleaving unitif the compressed frame has not yet been interleaved, and intermittentlyoutputting the compressed frame to a device on a reception side if thecompressed frame has been interleaved; a control unit for controllingthe interleaving operation in bit units of the interleaving unit, andthe compressing/intermittent transmitting operation of thecompressing/intermittent transmitting unit; the control unit controllingthe compressing/intermittent transmitting unit so that the compressedframe is divided to the front and rear of the same frame timing as inthe normal mode.

According to this invention, in the compressed mode, the compressedframe is divided to the front and rear of the same frame timing as inthe normal mode, and intermittently transmitted in that arrangement, andconsequently, an appropriate interleaving duration can be secured in thecompressed mode as in the normal mode using a simple interleavingconstitution so that the effects of transmission errors caused byinterleaving in bit units can be further reduced.

A spread spectrum communication device according to a next aspect of thepresent invention is characterized in that the control unit controls theinterleaving unit so that, in the compressed mode, interleaving in bitunits is performed across multiple frames.

According to this invention, in the compressed mode, since interleavingis controlled so that interleaving in bit units is performed acrossmultiple frames, an appropriate interleaving duration can be secured inthe compressed mode as in the normal mode, and consequently, the effectsof transmission errors caused by interleaving in bit units can befurther reduced.

A spread spectrum communication device according to a next aspect of thepresent invention is applied in a code division multiple access systemfor continuously transmitting multiple frames in a normal mode, andintermittently transmitting compressed frames in a compressed mode, andis characterized in that it comprises a compressing/intermittenttransmitting unit for compressing a frame, which comprises multipleslots and is a unit of a transmission data stream, and intermittentlytransmitting the compressed frame; and a control unit for controllingthe compressing/intermittent transmitting unit so as to slot thecompressed frame, and intermittently transmit the slotted frame in N (anatural number) slot units.

According to this invention, in the compressed mode, the compressedframe is slotted, and intermittently transmitted in N slot units, andtherefore, transmission power control bits transmitted in a downlink canbe received in comparatively short time intervals, whereby the amount oftransmission power control error can be reduced.

A spread spectrum communication device according to a next aspect of thepresent invention is characterized in that the control unit determinesthe N slot units in accordance with the relationship between themeasuring time of another frequency carrier component and the amount oftransmission power control error.

According to this invention, since the N slot units are determined inaccordance with the relationship between the measuring time of anotherfrequency carrier strength and the amount of transmission power controlerror, it is possible to secure time for reliably measuring the strengthof other frequency carriers, and in addition, the amount of transmissionpower control error can be greatly reduced.

A spread spectrum communication device according to a next aspect of thepresent invention is characterized in that it further has aninterleaving unit for interleaving in bit units a frame or a compressedframe, which is a unit of a transmission data stream, to minimizeeffects of transmission errors; the control unit controlling theinterleaving unit so that, in the compressed mode, interleaving in bitunits is performed across multiple frames.

According to this invention, in the compressed mode, since interleavingin bit units is controlled across multiple frames, an appropriateinterleaving duration can be secured in the compressed mode as in thenormal mode, and consequently, the effects of transmission errors causedby interleaving in bit units can be further reduced.

A spread spectrum communication device according to a next aspect of thepresent invention is applied in a code division multiple access systemfor continuously transmitting frames in a normal mode, andintermittently transmitting compressed frames in a compressed mode, andis characterized in that it comprises an interleaving unit forinterleaving in bit units a frame or a compressed frame, which is a unitof a transmission data stream, to minimize effects of transmissionerrors; a compressing/intermittent transmitting unit for compressing aframe prior to or after interleaving in the compressed mode, andmoreover, intermittently outputting the compressed frame to theinterleaving unit if the compressed frame has not yet been interleaved,and intermittently outputting the compressed frame to a device on areception side if the compressed frame has been interleaved; a controlunit for controlling the interleaving in bit units operation of theinterleaving unit, and the compressing/intermittent transmittingoperation of the compressing/intermittent transmitting unit; wherein inthe compressed mode, the control unit controls thecompressing/intermittent transmitting unit so that multiple frames priorto interleaving in bit units by the interleaving unit, or multipleframes after interleaving, are compressed using code-multiplexing in agiven frame timing.

According to this invention, in the compressed mode, multipleinterleaved frames are compressed using code-multiplexing in a givenframe timing and intermittently transmitted, whereby an appropriateinterleaving duration can be secured in the compressed mode as in thenormal mode, and consequently, performance deterioration caused byinterleaving in bit units can be prevented.

A spread spectrum communication device according to a next aspect of thepresent invention is characterized in that the control unit controls theinterleaving unit so that, in the compressed mode, interleaving isperformed in bit units across multiple frames.

According to this invention, in the compressed mode, interleaving isperformed in bit units across multiple frames, and therefore, a longerinterleaving duration can be secured in the compressed mode than in thenormal mode, whereby the effects of transmission errors caused byinterleaving in bit units can be further reduced. In particular, ifother frames are replaced by multi-code-transmitted frames andinterleaving is performed, it is possible to disperse multiplemulti-code-transmitted frames which are in error in the same place,thereby increasing the correcting capability of the error-correctionencoding.

A spread spectrum communication device according to a next aspect of thepresent invention is characterized in that the compressing/intermittenttransmitting unit has a memory size in correspondence with the number offrames to be code-multiplexed in the compressed mode.

According to this invention, since the memory size used is incorrespondence with the number of frames to be code-multiplexed in thecompressed mode, code-multiplexing can be realized reliably and withoutloss in the compressed mode.

A spread spectrum communication device according to a next aspect of thepresent invention is applied in a code division multiple access systemfor continuously transmitting frames in a normal mode, andintermittently transmitting compressed frames in a compressed mode, ischaracterized in that it comprises a compressing/intermittenttransmitting unit for compressing a frame, which is a unit of atransmission data stream, and intermittently transmitting the compressedframe, in the compressed mode; and a control unit for controlling thecompressing/intermittent transmitting unit so that, in the compressedmode, the compressing/intermittent transmitting unit intermittentlytransmits at a lower transmission rate than the transmission rate in thenormal mode, while using the same transmission power as in the normalmode.

According to this invention, in the compressed mode, thecompressing/intermittent transmitting unit intermittently transmits at alower transmission rate than the transmission rate in the normal mode,while using the same transmission power as in the normal mode, andconsequently, the there is less interference power on other users on thesame frequency during a frequency handover, enabling the frequencyhandover to be realized with reduced interference.

A spread spectrum communication device according to a next aspect of thepresent invention is characterized in that it further comprises aninterleaving unit for interleaving in bit units a frame or a compressedframe, which is a unit of a transmission data stream, to minimizeeffects of transmission errors; the control unit controlling theinterleaving unit so that, in the compressed mode, interleaving in bitunits is performed across multiple frames.

According to this invention, in the compressed mode, interleaving in bitunits is performed across multiple frames, and therefore an appropriateinterleaving duration can be secured in the compressed mode as in thenormal mode, and consequently, the effects of transmission errors causedby interleaving in bit units can be further reduced.

A spread spectrum communication device according to a next aspect of thepresent invention is characterized in that the control unit controls thecompressing/intermittent transmitting unit so that the compressed frameis divided to the front and rear of the same frame timing as in thenormal mode.

According to this invention, since the compressed frame is divided tothe front and rear of the same frame timing as in the normal mode, andintermittently transmitted in compliance with that arrangement, anappropriate interleaving duration can be secured in the compressed modeas in the normal mode with a simple interleave constitution, andconsequently, deterioration in performance caused by interleaving in bitunits can be further reduced.

A spread spectrum communication device according to a next aspect of thepresent invention is characterized in that the control unit controls thecompressing/intermittent transmitting unit so as to slot the compressedframe, and intermittently transmit the slotted frame in N (a naturalnumber) slot units.

According to this invention, in the compressed mode, the compressedframe is slotted and intermittently transmitted in N slot units;therefore, transmission power control bits transmitted in a downlink canbe received in comparatively short time intervals, whereby the amount oftransmission power control error can be reduced.

A spread spectrum communication device according to a next aspect of thepresent invention is applied in a code division multiple access systemfor continuously transmitting frames in a normal mode, andintermittently transmitting compressed frames in a compressed mode, andis characterized in that it comprises a memory unit for storing optimumtransmission power control units for the normal mode and the compressedmode, so that the transmission power control unit controlling one outputof transmission power is greater in the compressed mode than in thenormal mode; and a transmission power control unit for referring to thememory unit, and controlling transmission power to a communicationpartner device in compliance with transmission power control units incorrespondence with the normal mode and the compressed mode, based oninformation representing a reception power received from thecommunication partner device.

According to this invention, in the compressed mode, transmission powerto the communication partner device is controlled so that a transmissionpower control unit for one time is greater in the compressed mode thanin the normal mode, and consequently, in the compressed mode, even whenthe temporal intervals of the transmission power control duringintermittent transmission are wider, it is possible to widen the controlrange of the transmission power and maintain adhesion to thetransmission power in the compressed mode, whereby the amount of errorof transmission power control in the compressed mode can be reduced.

A spread spectrum communication device according to a next aspect of thepresent invention is characterized in that it further comprises acompressing/intermittent transmitting unit for compressing a frame,which comprises multiple slots and is a unit of a transmission datastream, and intermittently transmitting the compressed frame; and acontrol unit for controlling the compressing/intermittent transmittingunit so as to slot the compressed frame, and intermittently transmit theslotted frame in N (a natural number) slot units.

According to this invention, in the compressed mode, the compressedframe is slotted, and intermittently transmitted in N slot units, andtherefore, transmission power control bits transmitted in a downlink canbe received in comparatively short time intervals, whereby the amount oftransmission power control error can be reduced.

A spread spectrum communication device according to a next aspect of thepresent invention is applied in a code division multiple access systemfor continuously transmitting frames in a normal mode, andintermittently transmitting compressed frames in a compressed mode, andis characterized in that it comprises a memory unit for taking moremultiple types of transmission power control unit than in the normalmode, a transmission power control controlling one input of transmissionpower, including among the multiple types of transmission power controlunit a transmission power control unit which is greater than in thenormal mode, and storing optimum transmission power control units forthe normal mode and the compressed mode; a transmission power controlunit for referring to the memory unit, and controlling transmissionpower to a communication partner device in compliance with transmissionpower control units in correspondence with the normal mode and thecompressed mode, and in addition, in correspondence with temporalintervals in the transmission power control in the compressed mode,based on information representing a reception power received from acommunication partner device.

According to this invention, transmission power to a communicationpartner device is controlled in compliance with transmission powercontrol units in correspondence with the normal mode and the compressedmode, and in addition, in correspondence with temporal intervals in thetransmission power control in the compressed mode; therefore, even whenthe temporal intervals of the transmission power control duringintermittent transmission alter, by utilizing the control range of thetransmission power it is possible to maintain adhesion to thetransmission power in the compressed mode, thereby reducing the amountof error of transmission power control in the compressed mode.

A spread spectrum communication device according to a next aspect of thepresent invention is characterized in that it further comprises acompressing/intermittent transmitting unit for compressing a frame,which comprises multiple slots and is a unit of a transmission datastream, and intermittently transmitting the compressed frame; and acontrol unit for controlling the compressing/intermittent transmittingunit so as to slot the compressed frame, and intermittently transmit theslotted frame in N (a natural number) slot units.

According to this invention, in the compressed mode, the compressedframe is slotted, and intermittently transmitted in N slot units, andtherefore, transmission power control bits transmitted in a downlink canbe received in comparatively short time intervals, whereby the amount oftransmission power control error can be greatly reduced.

A spread spectrum communication device according to a next aspect of thepresent invention is applied in a code division multiple access systemfor continuously transmitting frames in a normal mode, andintermittently transmitting compressed frames in a compressed mode, andis characterized in that it comprises a transmission section for using adesired spreading code to create transmission data of a quantitycorresponding to a number of users who can be served thereby, incorrespondence with the normal mode and the compressed mode, and addingand transmitting the transmission data created in correspondence withthe number of users; and a compressed mode control section, connected tothe transmission section, for controlling the creation operation oftransmission data by the transmission section in the compressed mode;the compressed mode control section having a frame combining unit forextracting from given combinations of multiple compressed mode frames,compressed by separate users in the transmission section, a combinationhaving a total transmission duration of less than one frame duration; aspreading code allocation unit for allocating the same spreading code toeach of multiple channels which transmit the combination extracted bythe frame combining unit; and a transmission timing control unit forusing a single spreading code, allocated by the spreading codeallocating unit, to control the transmission section so thattransmission timings of multiple compressed mode frames, which comprisethe above extracted combination, do not temporally overlap within oneframe duration.

According to this invention, the compressed mode control sectionextracts from given combinations of multiple compressed mode frames,compressed by separate users in the transmission section, a combinationhaving a total transmission duration of less than one frame duration,allocates the same spreading code to each of multiple channels whichtransmit the combination extracted by the frame combining unit, and usesa single spreading code, allocated by the spreading code allocationunit, to control the transmission section so that transmission durationof multiple compressed mode frames, which comprise the above extractedcombination, do not temporally overlap within one frame duration;therefore, when there are multiple compressed mode frames, the number ofspreading codes with low spreading factor used in the compressed modecan be reduced, and consequently, the spreading code resources can beeffectively used in the compressed mode.

A spread spectrum communication device according to a next aspect of thepresent invention is applied in a code division multiple access systemfor continuously transmitting frames in a normal mode, andintermittently transmitting compressed frames in a compressed mode, andis characterized in that it comprises a compressing/intermittentreceiving unit for intermittently receiving a compressed frame in thecompressed mode; search code detecting and determining unit fordetecting on other frequency carriers, during non-transmission period inthe compressed mode, a first search code, which is shared at all basestations and is time-continually transmitted, and a second search code,which is transmitted at the same timing as the first search code and canbe identified by multiple numeric patterns, and determining these searchcodes based on a predetermined reference; a control unit for selectingthe compressing/intermittent receiving unit during intermittentreceiving, selecting the search code detecting and determining unitduring non-transmission duration, and controlling operations of both;the control unit establishing synchronization to the other frequencycarrier, based on the first search code and second search code detectedby the search code detecting and determining unit, and therebycontrolling a handover between different frequencies.

According to this invention, synchronization to another frequencycarrier is established based on the first search code and second searchcode detected by the search code detecting and determining unit, therebyenabling a handover to be efficiently performed between differentW-CDMA/W-CDMA frequencies.

A spread spectrum communication device according to a next aspect of thepresent invention is characterized in that the control unit carries outcontrol to detect at least one first search code during thenon-transmission period which is not more than half of one frame, andthereafter, carries out control to repeat the processing of shifting thenon-transmission period by a predetermined slot unit, and to detect anumeric value of all second search codes using multiple frames, and toestablish synchronization to the other frequency carrier, based on thedetected first search code and the numeric pattern of second searchcode, thereby controlling a handover between different frequencies.

According to this invention, at least one first search code is detectedduring the non-transmission period which is not more than half of oneframe, and thereafter, the processing of shifting the non-transmissionperiod by a predetermined slot unit is repeated, a numeric value of allthe second search codes is detected using multiple frames, andsynchronization is established to the other frequency carrier based onthe detected first search code and the numeric pattern of second searchcode, thereby enabling a handover to be even more efficiently performedbetween different W-CDMA/W-CDMA frequencies.

A spread spectrum communication device according to a next aspect of thepresent invention is characterized in that the non-transmission durationcan be arranged across multiple frames.

According to this invention, since the non-transmission period can bearranged across multiple frames, the second search codes can be detectedmultiple times, improving the reliability of the detected codes.

A spread spectrum communication device according to a next aspect of thepresent invention is characterized in that, when no search code can beobtained which satisfies a predetermined level of reliability during thesearch code detection, a search code is detected again in the place.

According to this invention, when no search code can be obtained whichsatisfies a predetermined level of reliability during the search codedetection, a search code is detected again in the place, andconsequently, synchronization can be established based on information ofhigh reliability.

A spread spectrum communication device according to a next aspect of thepresent invention is applied in a code division multiple access systemfor continuously transmitting frames in a normal mode, andintermittently transmitting compressed frames in a compressed mode, andis characterized in that it comprises a compressing/intermittentreceiving unit for intermittently receiving a compressed frame in thecompressed mode; information detecting and determining unit fordetecting in another communication system, during non-transmissionperiod in the compressed mode, a first information for matchingfrequencies, and a second information for achieving synchronization, anddetermining the first and second information based on a predeterminedreference; a control unit for selecting the compressing/intermittentreceiving unit during intermittent receiving, selecting the informationdetecting and determining unit during non-transmission period, andcontrolling operations of both; the control unit establishingsynchronization to the other communication system, based on the firstinformation and second information detected by the information detectingand determining unit, and thereby controlling a handover betweendifferent frequencies.

According to this invention, synchronization to another communicationsystem is established based on the first information and secondinformation detected by the information detecting and determining unit,thereby enabling a handover between different frequencies to be achievedefficiently.

A spread spectrum communication device according to a next aspect of thepresent invention is characterized in that the control unit carries outcontrol to detect at least one first information during thenon-transmission period which is not more than half of one frame,thereafter, carries out control to set the non-transmission period basedon a time found by the detected first information, and to detect thesecond information, and establishes synchronization to the othercommunication system, based on the detected first information and secondinformation, thereby controlling a handover between differentfrequencies.

According to this invention, at least one first information is detectedduring the non-transmission period which is not more than half of oneframe, thereafter, the non-transmission period is set based on a timefound by the detected first information, the second information isdetected, and synchronization to the other communication system isestablished based on the detected first information and secondinformation; therefore, a handover between different systems can becarried out more effectively.

A spread spectrum communication method according to a next aspect of thepresent invention is applied in a code division multiple access systemfor continuously transmitting frames in a normal mode, andintermittently transmitting compressed frames in a compressed mode, andis characterized in that it comprises a first step of interleaving ofinterleaving bit units across multiple frames, in order to minimizeeffects of transmission errors, in the compressed mode; a second step ofcompressing a frame interleaved in bit units in the first step, andintermittently transmitting it.

According to this invention, in the compressed mode, in order tominimize effects of transmission errors, interleaving of bit units isperformed across multiple frames, and the interleaved frame iscompressed and intermittently transmitted; therefore, an appropriateinterleaving duration can be secured in the compressed mode as in thenormal mode, and consequently, deterioration in performance caused byinterleaving in bit units can be prevented.

A spread spectrum communication method according to a next aspect of thepresent invention is applied in a code division multiple access systemfor continuously transmitting frames in a normal mode, andintermittently transmitting compressed frames in a compressed mode, andis characterized in that it comprises a first step of compressing aframe, which is a unit of a transmission data stream, and intermittentlyoutputting it, in the compressed mode; and a second step of interleavingbit units across a plurality of the compressed frames.

According to this invention, in the compressed mode, a frame, which is aunit of a transmission data stream, is compressed and outputintermittently, and interleaving in bit units is performed acrossmultiple compressed frames; consequently, therefore, an appropriateinterleaving duration can be secured in the compressed mode as in thenormal mode, and deterioration in performance caused by interleaving inbit units can be prevented.

A spread spectrum communication method according to a next aspect of thepresent invention is applied in a code division multiple access systemfor continuously transmitting frames in a normal mode, andintermittently transmitting compressed frames in a compressed mode, andis characterized in that it comprises a first step of interleaving bitunits of a frame, which is a unit of a transmission data stream, andintermittently outputting it, in order to minimize effects oftransmission errors; and a second step, performed in the compressedmode, of compressing a frame interleaved in bit units in the first step,dividing the compressed frame to the front and rear of the same frametiming as in the normal mode, and intermittently transmitting it.

According to this invention, in the compressed mode, a frame interleavedin bit units is compressed, divided to the front and rear of the sameframe timing as in the normal mode, and intermittently transmitted;consequently, an appropriate interleaving duration can be secured in thecompressed mode as in the normal mode, whereby performance deteriorationcaused by interleaving in bit units can be prevented.

A spread spectrum communication method according to the presentinvention is applied in a code division multiple access system forcontinuously transmitting frames in a normal mode, and intermittentlytransmitting compressed frames in a compressed mode, and ischaracterized in that it comprises a first step, performed in thecompressed mode, of compressing a frame, which is a unit of atransmission data stream, and interleaving bit units of the compressedframe; and a second step of dividing the compressed and interleavedframe to the front and rear of the same frame timing as in the normalmode, and intermittently transmitting it.

According to this invention, in the compressed mode, a frame, which is aunit of a transmission data stream, is compressed and interleaved in bitunits, divided to the front and rear of the same frame timing as in thenormal mode, and intermittently transmitted; consequently, anappropriate interleaving duration can be secured in the compressed modeas in the normal mode, whereby performance deterioration caused byinterleaving in bit units can be prevented.

A spread spectrum communication method according to a next aspect of thepresent invention is applied in a code division multiple access systemfor continuously transmitting frames in a normal mode, andintermittently transmitting compressed frames in a compressed mode, andis characterized in that it comprises a first step of dividing a frame,being a unit of a transmission data stream, into multiple slots in thecompressed mode; and a second step of intermittently transmitting theframe slotted in the first step in N (N=a natural number) slot units.

According to this invention, in the compressed mode, the compressedframe is slotted, and intermittently transmitted in N slot units, andtherefore, transmission power control bits transmitted in a downlink canbe received in comparatively short time intervals, whereby the amount oftransmission power control error can be greatly reduced.

A spread spectrum communication method according to a next aspect of thepresent invention is applied in a code division multiple access systemfor continuously transmitting frames in a normal mode, andintermittently transmitting compressed frames in a compressed mode, andis characterized in that it comprises a first step of interleaving inbit units a frame, being a unit of a transmission data stream, in orderto minimize effects of transmission errors; a second step, performed inthe compressed mode, of using code-multiplexing to compress, in a givenframe timing, multiple frames interleaved in bit units in the firststep, and transmit them intermittently.

According to this invention, in the compressed mode, code-multiplexingis used to compress, in a given frame timing, multiple framesinterleaved in bit units, and they are transmitted intermittently;consequently, an appropriate interleaving duration can be secured in thecompressed mode as in the normal mode, whereby performance deteriorationcaused by interleaving in bit units can be prevented.

A spread spectrum communication method according to a next aspect of thepresent invention is applied in a code division multiple access systemfor continuously transmitting frames in a normal mode, andintermittently transmitting compressed frames in a compressed mode, andis characterized in that it comprises a first step, performed in thecompressed mode, of using code-multiplexing to compress, in a givenframe timing, multiple frames interleaved in bit units in the firststep, and transmit them intermittently; and a second step ofinterleaving the compressed frames in bit units.

According to this invention, in the compressed mode, code-multiplexingis used to compress, in a given frame timing, multiple framesinterleaved in bit units, and they are transmitted intermittently;consequently, an appropriate interleaving duration can be secured in thecompressed mode as in the normal mode, whereby performance deteriorationcaused by interleaving in bit units can be prevented.

A spread spectrum communication method according to a next aspect of thepresent invention is applied in a code division multiple access systemfor continuously transmitting frames in a normal mode, andintermittently transmitting compressed frames in a compressed mode, andis characterized in that it comprises a first step of compressing aframe, which is a unit of a transmission data stream, in the compressedmode; and a second step of using the same transmission power as in thenormal mode to transmit the frame compressed in the first step at alower transmission rate than in the normal mode.

According to this invention, in the compressed mode, the sametransmission power as in the normal mode is used to intermittentlytransmit a compressed frame at a lower transmission rate than in thenormal mode; therefore, during a handover between frequencies, theamount of interference power to other users on the same frequency isreduced, whereby a handover between frequencies with reducedinterference can be achieved.

A spread spectrum communication method according to a next aspect of thepresent invention is applied in a code division multiple access systemfor continuously transmitting frames in a normal mode, andintermittently transmitting compressed frames in a compressed mode, andis characterized in that it comprises a first step of receivinginformation representing received power from a communication partnerdevice; a second step of preparing beforehand a table storing optimumtransmission power control units for the normal mode and the compressedmode, so that the transmission power control unit controlling one inputof transmission power is greater in the compressed mode than in thenormal mode, referring to the table, and determining transmission powerfor the normal mode and the compressed mode, based on the informationrepresenting received power received in the first step; and a third stepof transmitting to the communication partner device in compliance withthe transmission power determined in the second step.

According to this invention, by referring to a table storing optimumtransmission power control units for the normal mode and the compressedmode, so that the transmission power control unit controlling one inputof transmission power is greater in the compressed mode than in thenormal mode, based on the information representing received powerreceived from a communication partner device, transmission powers forthe normal mode and the compressed mode are determined, and in thecompressed mode, transmission is carried out so that the transmissionpower control unit controlling one input of transmission power isgreater in the compressed mode than in the normal mode; therefore, inthe compressed mode, even when the temporal intervals of thetransmission power control during intermittent transmission are wider,it is possible to widen the control range of the transmission power andmaintain adhesion to the transmission power in the compressed mode,whereby the amount of error of transmission power control in thecompressed mode can be reduced.

A spread spectrum communication method according to a next aspect of thepresent invention is applied in a code division multiple access systemfor continuously transmitting frames in a normal mode, andintermittently transmitting compressed frames in a compressed mode, andis characterized in that it comprises a first step of receivinginformation representing received power from a communication partnerdevice; a second step of taking more multiple types of transmissionpower control unit than in the normal mode, a transmission power controlcontrolling one input of transmission power, including among themultiple types of transmission power control unit a transmission powercontrol unit which is greater than in the normal mode, preparingbeforehand a table storing optimum transmission power control units forthe normal mode and the compressed mode, referring to the memory unit,and determining transmission power in correspondence with the normalmode and the compressed mode, and in addition, in correspondence withtemporal intervals in the transmission power control in the compressedmode, based on information representing a received power received in thefirst step; and a third step of transmitting to the communicationpartner device in compliance with the transmission power determined inthe second step.

According to this invention, with regard to a transmission power controlunit controlling one input of transmission power, more multiple types ofthese transmission power control units are taken than in the normalmode, including among the multiple types of transmission power controlunit a transmission power control unit which is greater than in thenormal mode, a table storing optimum transmission power control unitsfor the normal mode and the compressed mode is referred to, andtransmission power is determined in correspondence with the normal modeand the compressed mode and in addition, in correspondence with temporalintervals in the transmission power control in the compressed mode,based on information representing a reception power received from thecommunication partner device; and transmission is carried out incompliance with the determined transmission powers; therefore, in thecompressed mode, even when the temporal intervals of the transmissionpower control during intermittent transmission alter, by utilizing thecontrol range of the most suitable transmission power it is possible tomaintain adhesion to the transmission power, thereby reducing the amountof error of transmission power control in the compressed mode.

A spread spectrum communication method according to a next aspect of thepresent invention is applied in a code division multiple access systemfor continuously transmitting frames in a normal mode, andintermittently transmitting compressed frames in a compressed mode, andis characterized in that it comprises a first step of compressingframes, being units of a transmission data stream, in multipletransmission channels performing compressed mode transmission; a secondstep of extracting from given combinations of multiple compressed modeframes, compressed separately for users in the first step, a combinationhaving a total transmission duration of less than one frame duration; athird step of allocating the same spreading code to each of multiplechannels which transmit the combination extracted in the second step;and a fourth step of using the same spreading code, allocated in thethird step, to transmit multiple compressed mode frames, which comprisethe combination extracted in the second step, so that their transmissionduration do not temporally overlap within one frame duration.

According to this invention, in multiple transmission channels wherecompressed mode transmission is being performed, frames which are unitsof a transmission data stream are compressed; a combination having atotal transmission duration of less than one frame duration is extractedfrom given combinations of multiple compressed mode frames, compressedseparately for users; the same spreading code is allocated to each ofmultiple channels which transmit the extracted combination; and the samespreading code is used to transmit multiple compressed mode frames,comprising the extracted combination, so that their transmissionduration do not temporally overlap within one frame duration; therefore,the number of spreading codes with low spreading factor used in thecompressed mode can be reduced, and consequently, the spreading coderesources can be effectively used in the compressed mode.

A spread spectrum communication method according to a next aspect of thepresent invention is applied in a code division multiple access systemfor continuously transmitting frames in a normal mode, andintermittently transmitting compressed frames in a compressed mode, andis characterized in that it comprises a first search code detecting stepof detecting at least one first search code during the non-transmissionperiod which is not more than half of one frame; a second search codedetecting step of thereafter repeating the processing of shifting thenon-transmission period by a predetermined slot unit, and detecting anumeric value of all second search codes using multiple frames; ahandover between different frequencies being controlled by establishingsynchronization to another frequency carrier, based on the detectedfirst search code and the numeric pattern of second search code.

According to this invention, at least one first search code is detectedduring the non-transmission period which is not more than half of oneframe, thereafter, the process of shifting the non-transmission timingby a predetermined slot unit is repeated, a numeric value of all secondsearch codes is detected using multiple frames, and based on thedetected first search code and the numeric pattern of second searchcode, synchronization is established to another frequency carrier;consequently, a handover between different W-CDMA/W-CDMA frequencies canbe effectively performed.

A spread spectrum communication method according to a next aspect of thepresent invention is characterized in that the non-transmission periodcan be arranged across multiple frames.

According to this invention, since the non-transmission period can bearranged across multiple frames, the second search codes can be detectedmultiple times, improving the reliability of the detected codes.

A spread spectrum communication method according to a next aspect of thepresent invention is characterized in that, when no search code can beobtained which satisfies a predetermined level of reliability during thesearch code detection, a search code is detected again in the place.

According to this invention, when no search code can be obtained whichsatisfies a predetermined level of reliability during the search codedetection, a search code is detected again in the place, enablingsynchronization to be established based on information of highreliability.

A spread spectrum communication method according to a next aspect of thepresent invention is applied in a code division multiple access systemfor continuously transmitting frames in a normal mode, andintermittently transmitting compressed frames in a compressed mode, andis characterized in that it comprises a first information detecting stepof detecting a first information for matching frequencies duringnon-transmission period which is not more than half of one frame; asecond information detecting step of detecting second information forsetting the non-transmission duration, based on a known timingdetermined beforehand from the detected first information, and achievingsynchronization; a handover between different frequencies beingcontrolled by establishing synchronization to another communicationsystem, based on the detected first information and second information.

According to this invention, at least one first information is detectedduring the non-transmission period which is not more than half of oneframe, thereafter, the non-transmission period is set based on a knowntiming found by the detected first information, the second informationis detected, and synchronization to the other communication system isestablished based on the detected first information and secondinformation; therefore, a handover between different systems can becarried out more effectively.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a CDMA system according to a firstembodiment of the present invention;

FIG. 2 is a diagram explaining memory distribution of an interleaveraccording to the first embodiment;

FIG. 3 is a diagram explaining frame transmission of a downlinkaccording to the first embodiment;

FIG. 4 is a flowchart explaining a transmission operation in a normalmode according to the first embodiment;

FIG. 5 is a flowchart explaining a transmission operation in acompressed mode according to the first embodiment;

FIG. 6 is a flowchart explaining a reception operation in the normalmode according to the first embodiment;

FIG. 7 is a flowchart explaining a reception operation in the compressedmode according to the first embodiment;

FIG. 8 is a block diagram showing primary parts of a CDMA systemaccording to a second embodiment of the present invention;

FIG. 9 is a diagram explaining frame transmission of a downlinkaccording to the second embodiment;

FIG. 10 is a flowchart explaining a transmission operation in thecompressed mode according to the second embodiment;

FIG. 11 is a flowchart explaining a reception operation in thecompressed mode according to the second embodiment;

FIG. 12 is a diagram explaining frame transmission of a downlinkaccording to a third embodiment;

FIG. 13 is a flowchart explaining a transmission operation in thecompressed mode according to the third embodiment;

FIG. 14 is a flowchart explaining a reception operation in thecompressed mode according to the third embodiment;

FIG. 15 is a block diagram showing a CDMA system according to a fourthembodiment of the present invention;

FIG. 16 is a diagram explaining memory distribution of aframing/spreading unit according to the fourth embodiment;

FIG. 17 is a diagram explaining frame transmission of a downlinkaccording to the fourth embodiment;

FIG. 18 is a flowchart explaining a transmission operation in thecompressed mode according to the fourth embodiment;

FIG. 19 is a flowchart explaining a reception operation in compressedmode according to the fourth embodiment;

FIG. 20 is a block diagram of a COMA system according to a fifthembodiment of the present invention;

FIG. 21 is a diagram explaining frame transmission of a downlinkaccording to the fifth embodiment;

FIG. 22 is a flowchart explaining a transmission operation in thecompressed mode according to the fifth embodiment;

FIG. 23 is a flowchart explaining a reception operation in thecompressed mode according to the fifth embodiment;

FIG. 24 is a diagram explaining frame transmission of a downlinkaccording to a sixth embodiment of the present invention;

FIG. 25 is a flowchart explaining a transmission operation in thecompressed mode according to the sixth embodiment;

FIG. 26 is a flowchart explaining a reception operation in thecompressed mode according to the sixth embodiment;

FIG. 27 is a block diagram showing a COMA system according to a seventhembodiment of the present invention;

FIG. 28 is a diagram showing the relationship between transmission powercontrol symbol and transmission power control amount according to theseventh embodiment;

FIG. 29 is a flowchart explaining a transmission power control operationin the compressed mode according to the seventh embodiment;

FIG. 30 is a diagram showing the relationship between transmission powercontrol symbol and transmission power control amount according to aneighth embodiment of the present invention;

FIG. 31 is a flowchart explaining a transmission power control operationin the compressed mode according to the eighth embodiment;

FIG. 32 is a block diagram showing a CDMA system according to a ninthembodiment of the present invention;

FIG. 33 is a diagram explaining frame transmission of a downlinkaccording to the ninth embodiment;

FIG. 34 is a flowchart explaining a transmission power control operationin the compressed mode according to the ninth embodiment of the presentinvention;

FIG. 35 is a flowchart explaining a compressed mode control operationaccording to the ninth embodiment;

FIG. 36 is a diagram explaining conventional frame transmission of adownlink;

FIG. 37 is a diagram showing a frame constitution of a broadcast channel(BCH);

FIG. 38 is a detailed example of detecting a second search code insixteen consecutive slots;

FIG. 39 is a table showing a correspondence between the second searchcodes and the scrambling code groups;

FIG. 40 is a flowchart when synchronization establishment procedure iscarried out at the mobile station side;

FIG. 41 is a diagram showing a constitution of a receiver according to atenth embodiment of the present invention;

FIG. 42 is a diagram showing an outline of the operation of a receiveraccording to the present invention;

FIG. 43 is a flowchart when synchronization establishment procedure iscarried out at the mobile station side in a handover between differentfrequencies W-CDMA/W-CDMA;

FIG. 44 shows an example of obtaining a second search code;

FIG. 45 shows an example of obtaining a second search code;

FIG. 46 shows an example of obtaining a second search code;

FIG. 47 shows an example of obtaining a second search code;

FIG. 48 shows constitution of a GSM superframe; and

FIG. 49 is a flowchart when synchronization establishment procedure iscarried out at the mobile station side in a handover betweenW-CDMA/W-CDMA of different frequencies.

BEST MODES FOR CARRYING OUT THE INVENTION

To explain the present invention in more detail, it will be describedwith reference to the accompanying drawings.

To begin with, the constitution of a CDMA system will be explained. FIG.1 is a block diagram showing a CDMA system according to a firstembodiment of the present invention. The CDMA system comprises atransmitter 1A and a receiver 2A. Such a CDMA system is provided withboth base station and mobile stations. The base station and the mobilestations carry out radio communication using a CDMA communicationmethod.

The transmitter 1A, as shown in FIG. 1, comprises a controller 11A, anerror-correction encoder 12, an interleaver 13, a framing/spreading unit14A, a radio frequency transmitter 15, etc. Through negotiations withthe receiver 2A, the controller 11A principally controls the operationsof the interleaver 13, the framing/spreading unit 14A, and the radiofrequency transmitter 15. Through negotiations with the receiver 2A,this controller 11A instructs, using frame numbers, objects forinterleaving appropriate for a normal mode (a non-compressed mode) andcompressed mode. Furthermore, this controller 11A instructs atransmission timing to the framing/spreading unit 14A, in order toreduce the spreading factor and transmit a compressed mode frame in thecompressed mode. Furthermore, the controller 11A instructs to the radiofrequency transmitter 15 to increase the average transmission power whentransmitting the compressed mode frame.

The error-correction encoder 12 error-correct encodes the transmitteddata stream, thereby obtaining coded data. In order to be able tominimize the effect of transmission errors when continuous bits of atransmitted signal are lost or the like, for instance as a result offading, the interleaver 13 interleaves the temporal sequence of thecoded data in bit units.

This interleaver 13 has a memory for interleaving two frames. When thecontroller 11A has instructed frame number “1” for interleaving, theinterleaver 13 interleaves one frame in the normal mode. On the otherhand, when the frame number “2” has been instructed, the interleaver 13interleaves across two frames in the compressed mode.

The framing/spreading unit 14A spreads the band in correspondence withthe normal mode and the compressed mode, using a spreading code for eachuser, and forms a frame corresponding to each mode. When the controller11A has instructed transmission timing in correspondence with each ofthe modes, the framing/spreading unit 14A sends the frame to the radiofrequency transmitter 15 in accordance with the instructed transmissiontiming.

Furthermore, in the compressed mode, the framing/spreading unit 14Areceives a command from the controller 11A to reduce the spreadingfactor, and obtains a transmission signal using a lower spreading factorthan the normal mode, in accordance with that command. The radiofrequency transmitter 15 converts the transmission signal obtained bythe framing/spreading unit 14A to a radio frequency, and transmits it.In compliance with the controller 11A, this radio frequency transmitter15 outputs the transmission signal after increasing the averagetransmission power in the compressed mode to higher than that in thenormal mode.

As shown in FIG. 1, the receiver 2A comprises a controller 21A, anerror-correction decoder 22, a deinterleaver 23, adeframing/de-spreading unit 24A, a radio frequency receiver 25, etc.Through negotiations with the transmitter 1A, the controller 21Aprincipally controls the operations of the deinterleaver 23 and thedeframing/de-spreading unit 24A. Through negotiations with thetransmitter 1A, the controller 21A specifies, using frame numbers,objects for deinterleaving appropriate for the normal mode and thecompressed mode. Furthermore, this controller 21A instructs atransmission timing to the deframing/de-spreading unit 24A, in order toreduce the spreading factor and transmit a compressed mode frame in thecompressed mode. Furthermore, in the compressed mode, the controller 11Ainstructs to the radio frequency transmitter 15 a decrease in thespreading factor and a reception timing for receiving the compressedmode frame.

The radio frequency receiver 25 demodulates received signals sent froman antenna not shown in the diagram. The deframing/de-spreading unit 24Ade-spreads using spreading codes allocated to the users of the receiver2A in correspondence with normal mode and compressed mode, and creates aframe for each mode. When the controller 21A specifies the receptiontimings for each mode, the deframing/de-spreading unit 24A extracts areception signal from the radio frequency receiver 25 at the instructedtiming. Furthermore, in the compressed mode, the deframing/de-spreadingunit 24A receives a command from the controller 11A to reduce thespreading factor, and obtains a reception signal using a lower spreadingfactor than in the normal mode, in accordance with that command.

The deinterleaver 23 interleaves the temporal sequence of the coded datain bit units, in the reverse order to the interleaving in thetransmitter 1A (deinterleaving). Like the interleaver 13 mentionedabove, the deinterleaver 23 has a memory for deinterleaving two frames.When the controller 21A has instructed frame number “1” fordeinterleaving, the deinterleaver 23 deinterleaves one frame in normalmode. On the other hand, when the frame number “2” has been instructed,the deinterleaver 23 deinterleaves across two frames in the compressedmode. The error-correction decoder 22 error-correct decodes thedeinterleaved signal, thereby obtaining a decoded data, i.e. a receiveddata stream.

Next, the interleaver 13 and the deinterleaver 23 will be explained.FIG. 2 is a diagram explaining memory distribution of the interleaveraccording to the first embodiment, FIG. 2(a) illustrates the area usedin normal mode, and FIG. 2(b) illustrates the area used in compressedmode. In FIG. 2, a memory 131A provided with the interleaver 13 isshown. The deinterleaver 23 also comprises a memory having the samememory size as that of the interleaver 13. In the first embodiment,since interleaving is performed across two frames in the compressedmode, two-frame memory sizes in correspondence with an interleaving sizecorresponding to two frames are set in the interleaver 13 and thedeinterleaver 23 respectively.

When interleaving (see FIG. 2 (a)) in normal mode, only one frame (half)of the memory 131A is used, and interleaving is performed within thatframe. By contrast, in compressed mode (see FIG. 2 (b)), two frames(all) of the memory 131A are used, and interleaving is performed inthose two frames. Similarly, in the deinterleaver 23, the area of memoryused is altered in correspondence with the mode, as in the interleaver.

Next, frame transmission including compressed mode will be explained.FIG. 3 is a diagram explaining frame transmission of a downlinkaccording to the first embodiment. In FIG. 3, the vertical axisrepresents transmission rate/transmission power, and the horizontal axisrepresents time. Furthermore, in FIG. 3, F represents one frame. In aCDMA system, during normal transmission, a period of time is provided toslot the frame and transmit it intermittently, and the strength of theother frequency carriers is measured using non-transmission durationduring that period.

For this purpose, the slotted frame must be compressed, and as shown inFIG. 3, the transmission duration of a compressed frame is half of thenormal transmission duration. In this case, if interleaving is performedin the same manner as in normal transmission, there will only be halfthe necessary interleaving time, making it impossible to achieveadequate interleaving effects.

Accordingly, to secure sufficient time for interleaving, in compressedmode the transmitter 1A and the receiver 2A double the areas used in thememories of the interleaver 13 and the deinterleaver 23, and interleaveacross two frames. The interleaving time needed in compressed mode canbe determined easily from the ratio between the size of one frame andthe compressed mode frame.

Next, the transmission operation of the transmitter 1A will beexplained. FIG. 4 is a flowchart explaining a transmission operation innormal mode, and FIG. 5 is a flowchart explaining a transmissionoperation in compressed mode. The execution of the operations of FIG. 4and FIG. 5 is controlled by the controller 11A, the individualoperations being performed by various sections.

In the normal mode (see FIG. 4), frame number “1” is instructed to theinterleaver 13 (Step S101), and the interleaver 13 interleaves oneframe. Then, when the time reaches to a time required for transmittingone frame (Step S102), a transmission on next frame is instructed to theframing/spreading unit 14A (Step S103). In this way, in normal mode,frames are transmitted continuously.

Furthermore, in the compressed mode (see FIG. 5), multiple frames, thatis, frame number “2” is instructed to the interleaver 13 (Step S111),and the interleaver 13 interleaves across two frames. Then, when thetime reaches to a time required for transmitting a half-frame, that is,compressed mode frame timing (Step S112), a reduction in the spreadingfactor and a transmission timing are instructed to the framing/spreadingunit 14A (Step S113). Moreover, an increase in the average transmissionpower is instructed to the radio frequency transmitter 15 (Step S114).In this way, in the compressed mode, frames are transmittedintermittently (non-continuously).

Next, the reception operation of the receiver 2A will be explained. FIG.6 is a flowchart explaining the reception operation in normal mode, andFIG. 7 is a diagram explaining the reception operation in compressedmode. The operations of FIG. 6 and FIG. 7 are executed under the controlof the controller 21A although the individual operations are performedby various sections. In the normal mode (see FIG. 6), when the timereaches one frame timing (Step S121), a reception timing is instructedto the deframing/de-spreading unit 24A (Step S122). Then, a frame number“1” is instructed to the deinterleaver 23 (Step S123), and thedeinterleaver 23 deinterleaves one frame. In this way, in normal mode,frames are received continuously.

Furthermore, in the compressed mode (see FIG. 7), when the time reachesa half-frame, that is, compressed mode frame timing (Step S131), areduction in the spreading factor and a reception timing are instructedto deframing/de-spreading unit 24A (Step S132). Then, multiple frames,that is, frame number “2” is instructed to the deinterleaver 23 (StepS133), and the deinterleaver 23 deinterleaves across two frames. In thisway, in the compressed mode, frames are received intermittently(non-continuously).

As described above, according to the first embodiment, in compressedmode, interleaving bit units crossing multiple frames are controlled inorder to minimize the effects of transmission errors, thereby making itpossible to secure appropriate interleaving time in the compressed modeas in the normal mode. As a consequence, it is possible to prevent poorperformance caused by interleaving of bit units.

Furthermore, since the memory size corresponds to the number of framesto be interleaved in the compressed mode, it is possible to interleavebits units in a number of frames sufficient to minimize the effects oftransmission errors when transmission in the compressed mode.

In the first embodiment described above, the size of the memory forinterleaving and deinterleaving in the compressed mode is increased,securing an appropriate interleaving time in correspondence with thesize of the interleaving, but the present invention is not restricted tothis, and it is acceptable to secure an appropriate interleaving time bychanging the method of transmitting the compressed mode frame withoutincreasing the size of the memory, as in a second embodiment explainedlater. Since the entire constitution of the second embodiment of thepresent invention is the same as the first embodiment already explained,the following description covers only those features of the constitutionand operation which differ from the first embodiment. Furthermore,identical components are represented by the same reference numerals.

Here, only the primary constitution will be explained. FIG. 8 is a blockdiagram showing primary parts of a CDMA system according to the secondembodiment of the present invention. In the CDMA system of the secondembodiment, the difference from the first embodiment already describedis the size of the memory 131B of the interleaver 13, which here is oneframe. Furthermore, although not depicted in the diagram, thedeinterleaver 23 of the receiver also has a memory size of one frame, tomatch that of the interleaver 13.

Next, frame transmission including the compressed mode will beexplained. FIG. 9 is a diagram explaining frame transmission of adownlink according to the second embodiment. In FIG. 9, the verticalaxis represents transmission rate/transmission power, and the horizontalaxis represents time. In the CDMA system, during normal transmission, aperiod of time is provided to slot the frame and transmit itintermittently, and the strength of the other frequency carriers ismeasured using the fact that frames are not transmitted during thatperiod. For this purpose, the slotted frame must be compressed, but ifinterleaving is performed in the same manner as in normal transmission,the interleaving time will be insufficient, and it will be impossible toobtain an adequate interleaving effect.

Accordingly, the transmission timing of the compressed frame is divided,and one part is allocated to the head of the frame, the other isallocated to the end of the same frame, securing the desiredinterleaving time. At the receiver, this operation is performed inreverse. As in the first embodiment, the time needed for interleaving incompressed mode can be determined easily from the ratio between the sizeof one frame and the compressed mode frame.

Next, the operation will be explained. Here, only the operation incompressed mode will be explained. FIG. 10 is a flowchart explaining thetransmission operation in compressed mode, and FIG. 11 is a flowchartexplaining the reception operation in compressed mode. In the compressedmode (see FIG. 10) at the transmitter, interleaving in one frame isinstructed to the interleaver 13 (Step S201), and the interleaver 13interleaves one frame.

Then, when the time reaches any one of the front and rear timings of theone-frame timing (Step S202), a transmission timing is instructed to theframing/spreading unit 14A (Step S203). Moreover, an increase in theaverage transmission power is instructed to the radio frequencytransmitter 15 (Step S204), and the compressed mode frame isframe-transmitted at high transmission power. In this way, frames aretransmitted intermittently (non-continuously) in the compressed mode.

On the other hand, in the compressed mode at the receiver (see FIG. 11),when the time reaches any one of the front and rear timings of theone-frame timing (Step S211), a reception timing is instructed to thedeframing/de-spreading unit 24A (Step S212). Then, after the signal ofone frame has been received, a one-frame deinterleaving is instructed tothe deinterleaver 23 (Step S213), and the deinterleaver 23 deinterleavesone frame. In this way, frames are received intermittently(non-continuously) in the compressed mode.

As explained above, according to the second embodiment, in thecompressed mode, a frame which has been interleaved in bit units iscompressed, arranged into front and rear in the same frame timing as innormal mode, and intermittently transmitted in compliance with thatarrangement. Therefore, it is possible to secure an appropriateinterleaving time in compressed mode, in the same way as in normal mode,with a simple interleaving constitution. Consequently, poor performancecaused by interleaving in bit units can be prevented.

Furthermore, it is also possible in the second embodiment to prepare thememory sizes shown in FIG. 2, and control interleaving of bit unitscrossing multiple frames in the compressed mode. In this case, as in thefirst embodiment described above, it is possible to secure anappropriate interleaving time in the compressed mode, as in the normalmode, and to reduce transmission errors resulting from interleaving inbit units.

In the first embodiment already explained, to perform interleaving anddeinterleaving in the compressed mode, the size of memory is increasedand an interleaving time appropriate for the size of the interleaving issecured, but the present invention is not restricted to this, and it isacceptable to secure an appropriate interleaving time by a compressedmode frame transmission method different to that of the secondembodiment described above, as in a third embodiment described below.Since the entire constitution of the third embodiment of the presentinvention is the same as the second embodiment already explained, thefollowing description covers only those features of the operation whichdiffer from the second embodiment.

Firstly, frame transmission including compressed mode will be explained.FIG. 12 is a diagram explaining frame transmission of a downlinkaccording to the third embodiment. In FIG. 12, the vertical axisrepresents transmission rate/transmission power, and the horizontal axisrepresents time. In the CDMA system, during normal transmission, aperiod of time is provided to slot the frame and transmitintermittently, and the strength of other frequency carriers is measuredusing the fact that frames are not transmitted during that period. Forthis purpose, the slotted frame must be compressed, but if interleavingis performed in the same manner as in normal transmission, there willonly be half the necessary interleaving time, making it impossible toachieve adequate interleaving effects.

Accordingly, the transmission duration of the compressed frame isdivided in correspondence with multiple slots, and the non-transmissionperiod (idle period for measuring) is reduced so as not to affect thetransmission power control, securing the desired time for interleaving.In the receiver, this operation is performed in reverse. As in the firstembodiment, the time needed for interleaving in compressed mode can bedetermined easily from the ratio between the size of one frame and thecompressed mode frame.

Furthermore, the slot number N (where N is a natural number) forming thetransmission unit in compressed mode is determined in accordance withthe relationship between the measuring time of the strength of otherfrequency carriers and the transmission power control margin of error.For instance, when N=1 it indicates every slot, N=2 indicates every twoslots, and N=4 indicates every four slots. Here, N=1, 2, and 4 are justthe examples and it is also possible to handle other slot numbers.

Next, the operation will be explained. Here, only the operation incompressed mode will be explained. FIG. 13 is a flowchart explaining thetransmission operation in compressed mode, and FIG. 14 is a flowchartexplaining the reception operation in compressed mode. In the compressedmode at the transmitter (see FIG. 13), interleaving in one frame isinstructed to the interleaver 13 and the interleaver 13 interleaves oneframe (Step S301).

Then, when the time reaches the N slot timing which forms thetransmission unit in the compressed mode (Step S302), a transmissiontiming is instructed to the framing/spreading unit 14A (Step S303).Moreover, an increase in the average transmission power is instructed tothe radio frequency transmitter 15 (Step S304), and the compressed modeframe is frame-transmitted at high transmission power. In this way,frames are transmitted intermittently (non-continuously) in thecompressed mode.

On the other hand, in the compressed mode of the receiver (see FIG. 14),when the time reaches the N slot timing (Step S311), a reception timingis instructed to the deframing/de-spreading unit 24A (Step S312). Then,after the signal of one frame has been received, a one-framedeinterleaving is instructed to the deinterleaver 23 (Step S313), andthe deinterleaver 23 deinterleaves one frame. In this way, frames arereceived intermittently (non-continuously) in the compressed mode.

As explained above, according to the third embodiment, in the compressedmode, since a compressed frame is slotted and intermittently transmittedin N slot units, it is possible to receive transmission power controlbits transmission in the downlink in comparatively short time intervals.In this way, by controlling ON/OFF of each N slot, the margin of errorof transmission power control can be reduced.

In particular, since the N slot unit is determined in accordance withthe relationship between the measuring time of the strength of otherfrequency carriers and the transmission power control margin of error,it is possible to secure time in which the strength of other frequencycarriers can be reliably measured, and also to reduce the transmissionpower control margin of error.

Furthermore, it is also possible in the third embodiment to prepare thememory sizes shown in FIG. 2, and control interleaving of bit unitsacross multiple frames in the compressed mode. In this case, as in thefirst embodiment described above, it is possible to secure anappropriate interleaving time in the compressed mode, as in the normalmode, and to further reduce transmission errors resulting frominterleaving in bit units.

In the embodiments one to three described above, the frame timing waschanged in the normal mode and the compressed mode, but the presentinvention is not restricted to this, and it is acceptable tointermittently transmit with the same frame timing in compressed modeand normal mode, as in a fourth embodiment of the present inventiondescribed below.

Firstly, the constitution of the CDMA system will be explained. FIG. 15is a block diagram showing a CDMA system according to the fourthembodiment of the present invention. The CDMA system comprises atransmitter 1B and a receiver 2B. Such a CDMA system is provided withboth base station and mobile stations. The base station and the mobilestations carry out radio communication using a CDMA communicationmethod.

The transmitter 1B, as shown in FIG. 15, comprises a controller 11B, anerror-correction encoder 12, an interleaver 13, a framing/spreading unit14B, a radio frequency transmitter 15, etc. Through negotiations withthe receiver 2B, the controller 11B mainly controls the operations ofthe interleaver 13, the framing/spreading unit 14B, and the radiofrequency transmitter 15. In compressed mode, this controller 11Binstructs to the framing/spreading unit 14B multi-code transmission formultiple frames to be code-multiplexed and transmission timings fortransmitting compressed mode frames.

The error-correction encoder 12, the interleaver 13, and the radiofrequency transmitter 15 are the same as in the first embodiment alreadydescribed above, and explanation thereof will be omitted. As regards theinterleaver 13, it has a memory for interleaving one frame.

The framing/spreading unit 14B spreads the band in correspondence withnormal mode and compressed mode, using a spreading code for each user,and forms a frame corresponding to each mode. When the controller 11Bhas instructed transmission timing in correspondence with each of themodes, the framing/spreading unit 14B sends the frame to the radiofrequency transmitter 15 in accordance with the instructed transmissiontiming. Furthermore, in the compressed mode, the framing/spreading unit14B receives a command for multi-code transmission from the controller11B, and code-multiplexes two post-interleave frames in accordance withthat command.

In order to code-multiplex two frames, the framing/spreading unit 14Bhas a one-frame memory. That is, the interleaver 13 and theframing/spreading unit 14B each comprise a one-frame memory, enablingtwo frames to be code-multiplexed using a total memory size equivalentto two frames.

The receiver 2B, as shown in FIG. 15, comprises a controller 21B, anerror-correction decoder 22, a deinterleaver 23, adeframing/de-spreading unit 24B, a radio frequency receiver 25, etc.Through negotiations with the transmitter 1B, the controller 21B mainlycontrols the operations of the deinterleaver 23 and thedeframing/de-spreading unit 24B. In the compressed mode, this controller21B instructs the deframing/de-spreading unit 24B of reception timingsfor receiving multi-code transmission and compressed mode frames.

The error-correction decoder 22, the deinterleaver 23, and the radiofrequency transmitter 25 are the same as in the first embodiment alreadydescribed above, and explanation thereof will be omitted. As regards thedeinterleaver 23, it has a memory for interleaving one frame.

Like the framing/spreading unit 14B described above, thedeframing/de-spreading unit 24B comprises a one-frame memory fordeframing. When the controller 21B has instructed a reception timing incorrespondence with each of the modes, the deframing/de-spreading unit24B extracts the reception signal from the radio frequency transmitter25 in accordance with that reception timing. Furthermore, in thecompressed mode, the deframing/de-spreading unit 24B receives a commandfor multi-code transmission from the controller 21B, separates thede-spread data into frame units in accordance with that command, andoutputs the frames in sequence to the deinterleaver 23.

Next, the primary constitution of the framing/spreading unit 14B and thedeframing/de-spreading unit 24B will be explained. FIG. 16 is a diagramexplaining memory distribution of the framing/spreading unit 14Baccording to the fourth embodiment, wherein FIG. 16(a) illustrates thearea used in normal mode, and FIG. 16(b) illustrates the area used incompressed mode. In FIG. 16, the framing/spreading unit 14B has a memory141A. The deframing/de-spreading unit 24B also has a memory of the samememory size as that of the framing/spreading unit 14B.

In the fourth embodiment, since code-multiplexing is performed acrosstwo frames in the compressed mode, a one-frame memory size, incorrespondence with a two-frame code-multiplexing size, is set in theboth framing/spreading unit 14B and the deframing/de-spreading unit 24B.In fact, two-frame framing and deframing can be achieved using theone-frame memories of the interleaver 13 the deinterleaver 23.

In normal mode (see FIG. 16 (a)), since code-multiplexing is not needed,framing and the like is carried out based on data interleaved by theinterleaver 13 without using the memory 141A. On the contrary, incompressed mode (see FIG. 16 (b)), a two-frame memory size is requiredto perform code multiplexing, and therefore the memory 141A of theframing/spreading unit 14B is used in addition to the memory of theinterleaver 13. Similarly, whether the memory is used or not in thedeframing/de-spreading unit 24B also varies depending on the mode.

Next, frame transmission including compressed mode will be explained.FIG. 17 is a diagram explaining frame transmission of a downlinkaccording to the fourth embodiment. In FIG. 17, the vertical axisrepresents transmission rate/transmission power, and the horizontal axisrepresents time. Furthermore, in FIG. 17, F represents one frame. In theCDMA system, during normal transmission, a period of time is provided toslot the frame and transmit it intermittently, and the strength of otherfrequency carriers is measured using the fact that a frame is nottransmitted during that period.

For this purpose, the slotted frame must be compressed, and inconventional methods, the transmission duration of a compressed framebecomes half of the normal transmission duration. In this case, ifinterleaving is performed in the same manner as in normal transmission,there will only be half of the necessary interleaving time, making itimpossible to achieve adequate interleaving effects.

Accordingly, the transmitter 1B performs interleaving of the same sizeas in the normal mode, and code-multiplexes multiple frames in the frametiming, in order to secure the same timing for interleaving in thecompressed mode as in the normal mode, in compressed mode. For instance,in the example shown in FIG. 17, in normal transmission (normal mode),post-interleaving frames are transmitted in a sequence of frames #1, #2,and thereafter, in slotted transmission (compressed mode), individuallyinterleaved frames #3 and #4 are code-multiplexed together, andcompressed frames are transmitted.

Next, the operation will be explained. Since the transmission andreception is performed in the same manner as the conventional methods,explanation thereof will be omitted. Firstly, the transmission operationof the transmitter 1B will be explained. FIG. 18 is a flowchartexplaining the transmission operation in compressed mode. The executionof the operation of FIG. 18 is controlled by the controller 11B althoughindividual operations are performed by various sections. In thecompressed mode, interleaving in one frame is instructed to theinterleaver 13 (Step S401), and the interleaver 13 interleaves in oneframe.

Then, when the time reaches a given frame timing for multi-codetransmission (Step S402), multi-code transmission and transmissiontimings are instructed to the framing/spreading unit 14B (Step S403).Consequently, the framing/spreading unit 14B code-multiplexes twoframes. In this way, in the compressed mode, frames are transmittedintermittently (non-continuously).

Next, the reception operation of the receiver 2B will be explained. FIG.19 is a flowchart explaining the reception operation in the compressedmode. The execution of the operation of FIG. 19 is controlled by thecontroller 21B although individual operations are performed by varioussections. In the compressed mode, when the time reaches the frame timingfor the multi-code transmission described above (Step S411), frameseparation of received code-multiplexed data and a reception timing areinstructed to the deframing/de-spreading unit 24B (Step S412).

Then, deinterleaving in the separated frames is instructed to thedeinterleaver 23 (Step S413), and the deinterleaver 23 deinterleaves oneframe. In this way, in the compressed mode, frames are receivedintermittently (non-continuously).

As described above, according to the fourth embodiment, in thecompressed mode, multiple frames which have been interleaved in bitunits to minimize the effects of transmission errors are compressed bycode division multiplexing in the given frame timing prior totransmission. Therefore, it is possible to secure an appropriateinterleaving time in the same way and using the same constitution in thecompressed mode and the normal mode. In this way, by controlling ON/OFFin each compressed mode frame, poor performance caused by interleavingin bit units can be prevented.

Furthermore, since the memory size used corresponds to the number offrames to be code-multiplexed in the compressed mode, code-multiplexingcan be performed reliably and without loss in the compressed mode.

Furthermore, it is also possible in the fourth embodiment to controlinterleaving of bit units across multiple frames in the compressed modein the way as the first embodiment described above. In this case, it ispossible to secure a longer time for interleaving by increasing the sizeof the memories of the interleaver and the deinterleaver in compressedmode than in the normal mode. As a consequence, transmission errorsresulting from interleaving in bit units can be reduced. In particular,when code-multiplexed frames are interleaved by replacing other frames,places where multiple code-multiplexed frames are in error can bedispersed, improving the correcting result of the error-correctioncoding.

In the embodiments 1 to 4 described above, transmission power isincreased in order to transmit frames in the compressed mode withoutinformation loss, but the present invention is not restricted to this,and it is acceptable to determine the amount of the transmission powerafter considering interference on other user channels caused by theamount of the transmission power, as described below in a fifthembodiment.

Firstly, the constitution of the CDMA system will be explained. FIG. 20is a block diagram showing a CDMA system according to a fifth embodimentof the present invention. The CDMA system comprises a transmitter 1C anda receiver 2C. Such a CDMA system is provided with both base station andmobile stations. The base station and the mobile stations carry outradio communication using a CDMA communication method.

As shown in FIG. 20, the transmitter 1C comprises a controller 11C, anerror-correction encoder 12, an interleaver 13, a framing/spreading unit14C, a radio frequency transmitter 15, etc. Through negotiations withthe receiver 2C, the controller 11C mainly controls the operations ofthe interleaver 13, the framing/spreading unit 14C, and the radiofrequency transmitter 15. In compressed mode, this controller 11Cinstructs to the framing/spreading unit 14C a reduction of informationrate and transmission timings for transmitting compressed mode frames.Furthermore, this controller 11C differs from the one in embodiments 1to 4 described above in that it does not generate a command to the radiofrequency transmitter 15 to raise the transmission power in thecompressed mode.

The error-correction encoder 12, the interleaver 13, and the radiofrequency transmitter 15 are the same as in the first embodiment alreadydescribed above, and explanation thereof will be omitted. As regards theinterleaver 13, it has a memory for interleaving one frame.

The framing/spreading unit 14C spreads the band in correspondence withnormal mode and compressed mode, using a spreading code for each user,and forms a frame corresponding to each mode. When the controller 11Chas instructed a transmission timing in correspondence with each of themode, the framing/spreading unit 14C sends the frame to the radiofrequency transmitter 15 in accordance with that transmission timing.Furthermore, in the compressed mode, when the framing/spreading unit 14Creceive a command to reduce the information rate from the controller 11Cthen it compresses the insufficiently interleaved frame to form acompressed mode frame in compliance with that command.

As shown in FIG. 20, the receiver 2C comprises a controller 21C, anerror-correction decoder 22, a deinterleaver 23, adeframing/de-spreading unit 24C, a radio frequency transmitter 25, etc.Through negotiations with the transmitter 1C, the controller 21C mainlycontrols the operations of the deinterleaver 23 and thedeframing/de-spreading unit 24C. In the compressed mode, this controller21C instructs to the deframing/de-spreading unit 24C a reduction ininformation rate and reception timings for receiving compressed modeframes.

The error-correction decoder 22, the deinterleaver 23, and the radiofrequency transmitter 25 are the same as in the first embodiment alreadydescribed above, and explanation thereof will be omitted. As regards thedeinterleaver 23, it has a memory for interleaving one frame.

When the controller 21C has instructed a reception timing incorrespondence with each of the modes, the deframing/de-spreading unit24C extracts the received signal from the radio frequency transmitter 25in accordance with that reception timing. Furthermore, in the compressedmode, when the deframing/de-spreading unit 24C receives a command toreduce information rate from the controller 21C then it lowers theinformation rate in accordance with that command, performs framing andde-spreading, and outputs the frames in sequence to the deinterleaver23.

Next, frame transmission including compressed mode will be explained.FIG. 21 is a diagram explaining frame transmission of a downlinkaccording to the fifth embodiment. In FIG. 21, the vertical axisrepresents transmission rate/transmission power, and the horizontal axisrepresents time. In the CDMA system, during normal transmission, aperiod of time is provided to slot the frame and transmit itintermittently, and the strength of other frequency carriers is measuredusing the fact that a frame is not transmitted during that period. Forthat purpose, the slotted frame must be compressed, and in aconventional method, the transmission power is increased whentransmitting the compressed frame. In this case, amount of interferencepower to other user channels increases, leading to deterioration intransmission.

Accordingly, as shown in FIG. 21, when the same transmission power issecured in the compressed mode as in the normal mode, lowering thetransmission rate by a corresponding amount, and an interleavedtransmission frame is sent across multiple compressed mode frames, it ispossible to realize a handover between frequencies with reducedinterference.

Next, the operation will be explained. Since the transmission andreception is performed in the same manner as the conventional methods,explanation thereof will be omitted. Firstly, the transmission operationof the transmitter 1C will be explained. FIG. 22 is a flowchartexplaining the transmission operation in the compressed mode. Theexecution of the operation of FIG. 22 is controlled by the controller11C although the individual operations are performed by varioussections. In the compressed mode, interleaving in one frame isinstructed to the interleaver 13 (Step S501), and the interleaver 13interleaves in one frame.

Then, when the time reaches the compressed mode frame timing (StepS502), reduction of transmission rate and a transmission timing areinstructed to the framing/spreading unit 14C (Step S503). Consequently,the frame is transmitted at a lower transmission rate in the compressedmode time. In this way, in the compressed mode, frames are transmittedintermittently (non-continuously).

Next, the reception operation of the receiver 2C will be explained. FIG.23 is a flowchart explaining the reception operation in the compressedmode. The execution of the operation of FIG. 23 is controlled by thecontroller 21C although the individual operations are performed byvarious sections. In the compressed mode, when the time reaches thecompressed mode frame timing (Step S511), a reduction of transmissionrate and a reception timing are instructed to the deframing/de-spreadingunit 24C (Step S512).

Then, deinterleaving in the one frame is instructed to the deinterleaver23 (Step S513), and the deinterleaver 23 deinterleaves one frame. Inthis way, in the compressed mode, frames are received intermittently(non-continuously).

As described above, according to the fifth embodiment, in the compressedmode, compressed frames are intermittently transmitted at a transmissionrate which is lower than the transmission rate in the normal mode whileusing the same transmission power as in the normal mode. Therefore,during the frequency handover, the amount of interference power to otherusers on the same frequency is reduced. Consequently, it is possible torealize a handover between frequencies with less interference.

Furthermore, in the fifth embodiment, in the compressed mode, acompressed frame may be divided into the front and rear of the sameframe timing as in the normal mode, and transmitted intermittently incompliance with that arrangement, as in the second embodiment describedabove. Because of this fact, it is possible to secure an appropriateinterleaving time in compressed mode in the same way as in the normalmode, with a simple interleave constitution. As a result, poorperformance caused by interleaving in bit units can be prevented.

Furthermore, in the fifth embodiment, in the compressed mode, acompressed frame may be slotted and transmitted intermittently in N slotunits in the same manner as in the third embodiment described above.Because of this fact, it is possible to receive transmission powercontrol bits transmitted in the downlink in comparatively short timeintervals. As a result, the amount of error in the transmission powercontrol can be reduced.

In the fifth embodiment described above, one frame was interleaved, butthe present invention is not restricted to this, and it is acceptable toprevent compression in the interleaving time by interleaving acrossmultiple frames. With the exception of increase the memory size of theinterleaver, as in the first embodiment, the sixth embodiment has thesame overall constitution as the fifth embodiment described above, andso only the differing aspects of the operation will be explained below.

Accordingly, frame transmission including compressed mode will beexplained. FIG. 24 is a diagram explaining frame transmission of adownlink according to the sixth embodiment. In FIG. 24, the verticalaxis represents transmission rate/transmission power, and the horizontalaxis represents time. The difference with the fifth embodiment describedabove is that, as shown in FIG. 24, the interleaving is carried outacross multiple frames, i.e. two frames if the compressed mode frame isa ½ frame. Consequently, deterioration of decoding caused by compressingthe interleaving time can be reduced.

Next, the operation will be explained. Since the transmission andreception is performed in the same manner as in the conventionalmethods, explanation thereof will be omitted. Firstly, the transmissionoperation of the transmitter of the sixth embodiment will be explained.FIG. 25 is a flowchart explaining the transmission operation in thecompressed mode. The execution of the operation of FIG. 25 is controlledby the controller 11C although the individual operations are performedby various sections. In the compressed mode, interleaving across twoframes is instructed to the interleaver 13 (Step S601), and theinterleaver 13 interleaves two frames.

Then, when the time reaches the compressed mode frame timing (StepS602), reduction of transmission rate and a transmission timing areinstructed to the framing/spreading unit 14C (Step S603). Consequently,the frame is transmitted at a lower transmission rate in the compressedmode time. In this way, in the compressed mode, frames are transmittedintermittently (non-continuously).

Next, the reception operation according to the receiver of the sixthembodiment will be explained. FIG. 26 is a flowchart explaining areception operation in the compressed mode. The execution of theoperation of FIG. 26 is controlled by the controller 21C although theindividual operations are performed by various sections. In thecompressed mode, when the time reaches the compressed mode frame timing(Step S611), a reduction of transmission rate and a reception timing areinstructed to the deframing/de-spreading unit 24C (Step S612).

Then, deinterleave across two frames is instructed to the deinterleaver23 (Step S613), and the deinterleaver 23 deinterleaves across twoframes. In this way, in the compressed mode, frames are receivedintermittently (non-continuously).

As described above, according to the sixth embodiment, in addition towhat has been described in the fifth embodiment described above, in thecompressed mode, bit units are interleaved across multiple frames,enabling an appropriate interleaving time to be secured in thecompressed mode as in the normal mode. As a consequence, transmissionerrors caused by interleaving of bit units can be further reduced.

Furthermore, in the sixth embodiment, in the compressed mode, acompressed frame may be divided into the front and rear of the sameframe timing as in the normal mode, and transmitted intermittently incompliance with that arrangement in the same manner as in the secondembodiment described above. Because of this fact, it is possible tosecure an appropriate interleaving time in compressed mode in the sameway as in the normal mode, with a simple interleaving constitution. As aresult, poor performance caused by interleaving in bit units can beprevented.

Furthermore, in the sixth embodiment, in the compressed mode, acompressed frame may be slotted and transmitted intermittently in N slotunits in the same manner as in the third embodiment described above.Because of this act, it is possible to receive transmission powercontrol bits transmitted in the downlink in comparatively short timeintervals. As a result, the amount of error in the transmission powercontrol can be reduced.

In the above-mentioned embodiments 1 to 6, a function for preventingtransmission deterioration in the compressed mode was explained, but thepresent invention is not restricted to this, and it is acceptable tovary the amount of transmission power during transmission power controlas in a seventh embodiment described below.

Firstly, the constitution of the CDMA system will be explained. FIG. 27is a block diagram showing a CDMA system according to a seventhembodiment of the present invention. The CDMA system comprises atransmitter 1D and a receiver 2D. Such a CDMA system is provided withboth the base station and mobile stations. The base station and themobile stations carry out radio communication using a CDMA communicationmethod.

As shown in FIG. 27, the transmitter 1D comprises a controller 11D, anerror-correction encoder 12, an interleaver 13, a framing/spreading unit14D, a radio frequency transmitter 15, etc. Through negotiations withthe receiver 2D, the controller 11D mainly controls the operations ofthe interleaver 13, the framing/spreading unit 14D, and the radiofrequency transmitter 15. This controller 11D supplies compressed modeinformation such as transmission timings in compressed mode to theframing/spreading unit 14D. Furthermore, this controller 11D instructsincrease or decrease of the transmission power to the radio frequencytransmitter 15, based on received power information and TPC bitinformation received from the receiver 2D via an uplink.

The error-correction encoder 12, the interleaver 13, and the radiofrequency transmitter 15 are the same as in the first embodiment alreadydescribed above, and explanation thereof will be omitted. As regards theinterleaver 13, it has a memory for interleaving one frame. Furthermore,the radio frequency transmitter 15 increase or decreases thetransmission power in accordance with the transmission power increase ordecrease instruction of the controller 11D, and outputs the transmissionsignals.

The framing/spreading unit 14D is assigned operations such as spreadingthe band in correspondence with the normal mode and compressed mode,using a spreading code for each user, forming a frame corresponding toeach mode, and, when the controller 11D has instructed a transmissiontiming in correspondence with each of the modes, sending the frame tothe radio frequency transmitter 15 in accordance with that transmissiontiming.

As shown in FIG. 27, the receiver 2D comprises a controller 21D, anerror-correction decoder 22, a deinterleaver 23, adeframing/de-spreading unit 24D, a radio frequency transmitter 25, etc.Through negotiations with the transmitter 1D, the controller 21D mainlycontrols the operations of the deinterleaver 23 and thedeframing/de-spreading unit 24D. In the compressed mode, this controller21D supplies compressed frame information, such as reception timings andthe like for receiving compressed mode frames, to thedeframing/de-spreading unit 24D.

The error-correction decoder 22, the deinterleaver 23, and the radiofrequency transmitter 25 are the same as in the first embodiment alreadydescribed above, and explanation thereof will be omitted. Here, thedeinterleaver 23 has a memory for interleaving one frame. Furthermore,when the radio frequency receiver 25 has received a reception signal, itnotifies the controller 21D of information (information on receptionpower) showing the reception power.

When the deframing/de-spreading unit 24D has received reception timingsin correspondence with each of the modes from the controller 21D, itextracts the reception signal from the radio frequency transmitter 25 inaccordance with the reception timings. Furthermore, in the compressedmode, this deframing/de-spreading unit 24D receives compressed frameinformation from the controller 21D and performs deframing andde-spreading, and sequentially outputs the frames to the deinterleaver23. Furthermore, the deframing/de-spreading unit 24D detects TPC bitsfrom the received signal, and notifies the controller 21D of these.

Next, the relationship between the TPC bits and the transmission powercontrol amount will be explained. FIG. 28 is a diagram showing therelationship between transmission power control symbols and transmissionpower control amounts according to the seventh embodiment. The tableshown in FIG. 28 is held by the controller 11D of the transmitter 1D andalso the controller 21D of the receiver 2D. The TPC bit is thetransmission power control symbol, and since it comprises one bit, ithas two states: 1 (ON) and 0 (OFF). In the normal mode, a transmissionpower control amount of +1.0 dB (decibel) is applied in the 1 (ON) stateand a transmission power control amount of −1.0 dB is applied in the 0(OFF) state. That is, the unit of transmission power control in thenormal mode is 1 dB.

On the other hand, in the compressed mode, a transmission power controlamount of +3.0 dB (decibels) is applied in the 1 (ON) state, and atransmission power control amount of −3.0 dB is applied in the 0 (OFF)state. That is, the unit of transmission power control in the normalmode is 3 dB. The transmission power control unit used in the compressedmode has a greater absolute value than that used in the normal mode, forthe reason that idle period (non-transmission timing) in the compressedmode lowers the adhesion capability to the transmission power control.

Next, the operation will be explained. The seventh embodiment differsfrom the other embodiments in respect of its transmission power controlfunction, and therefore only the transmission power control will beexplained. FIG. 29 is a flowchart explaining the transmission powercontrol operation in compressed mode according to the seventhembodiment. Transmission power control of the transmitter 1D and thereceiver 2D explained here is the transmission power control to anuplink.

A TPC bit from the receiver 2D and reception power information on thereceiver 2D side are sent to the transmitter 1D. In the transmitter 1D,when the TPC bit and the reception power information are received (StepS701), transmission power increase/decrease information is determinedbased on this received information (Step S702). Then, transmission fromthe radio frequency transmitter 15 is controlled at that determinedtransmission power (Step S703).

More specifically, for instance, when there is one TPC bit, aninstruction is made to increase the transmission power, and consequentlythe transmission power control of +3 dB from the table of FIG. 29 isset. Therefore, an instruction to transmit after raising the presenttransmission power by 3 dB is sent to the radio frequency transmitter15. On the other hand, when the TPC bit is 0, an instruction is given todecrease the transmission power, by setting the transmission powercontrol of −3 dB from the table of FIG. 28. Therefore, an instruction totransmit after decreasing the present transmission power by 3 dB is sentto the radio frequency transmitter 15.

As described above, according to the seventh embodiment, in thecompressed mode, transmission power is controlled so that thetransmission power control unit for one transmission is greater than inthe normal mode, and consequently, even when the temporal intervals ofthe transmission power control during intermittent transmission arewider, it is possible to widen the control range of the transmissionpower and maintain adhesion to the transmission power in the compressedmode. As a consequence, the amount of error of transmission powercontrol in the compressed mode can be reduced.

Furthermore, in the seventh embodiment, in the compressed mode, acompressed frame may be slotted and transmitted intermittently in N slotunits in the same manner as in the third embodiment described above.Consequently, it is possible to transmit transmission power control bitsin the downlink in comparatively short time intervals. As a result, theamount of error in the transmission power control can be reduced.

In the above-mentioned seventh embodiment, the TPC bit states werelimited to two types of increase and decrease, but the present inventionis not restricted to this, and it is acceptable to vary the amount oftransmission power control for each mode, as in an eighth embodimentexplained below. The eighth embodiment has the same overall constitutionas the seventh embodiment described above, and so only the differingaspects of the operation will be explained below. In the followingexplanation, the reference numerals of FIG. 27 will be used.

Firstly, the relationship between the TPC bits and the transmissionpower control amount will be explained. FIG. 30 is a diagram showing therelationship between transmission power control symbols and transmissionpower control amounts according to the eighth embodiment. The tableshown in FIG. 30 is held by the controller 11D of the transmitter 1D andalso the controller 21D of the receiver 2D.

In the eighth embodiment, the TPC bit is the transmission power controlsymbol, and there are two bits. Therefore, there are four types ofstates: (11B (B represents a binary number), 10B, 01B, and 00B). The twoTPC bit states 11B and 10B represent an increase of transmission power,and the two TPC bit states 01B and 00B represent a decrease oftransmission power.

In the normal mode, as in the seventh embodiment described above, thereare only two types of states, ON and OFF. However, since two TPC bitsare used, ON is 11B and OFF is 00B. When the TPC bits are 11B thetransmission power control amount is +1 dB, and when they are 00B thetransmission power control amount is −1 dB. Similarly, in the compressedmode, as in the seventh embodiment described above, when the TPC bitsare 11B the transmission power control amount is increased by threetimes the transmission power control amount in the normal mode, namely+3 dB. When the TPC bits are 00B the transmission power control amountis increased by three times of the transmission power control amount inthe normal mode, namely −3 dB. In the eighth embodiment, four types ofvariation are applied to the transmission power control amount in thecompressed mode, so that when the TPC bits are 10B the transmissionpower control amount is +1 dB, and when they are 01B the transmissionpower control amount is −1 dB.

In the normal mode, when the TPC bits are in the 11B state, atransmission power control amount of +1.0 dB (decibels) is applied, andin the 00B state, a transmission power control amount of −1.0 dB isapplied. That is, the unit of transmission power control in the normalmode is 1 dB. In the normal mode, there are no stipulations concerningthe state 10B and the state 01B, and the transmission power remains inits current state during this mode.

On the other hand, in the compressed mode, when the TPC bits are 11B, atransmission power control amount of +3.0 dB (decibels) is applied, andwhen the TPC bits are 00B, a transmission power control amount of −3.0dB is applied. That is, when the TPC bits are at 11B or 00B, the unit oftransmission power control in the normal mode is 3 dB.

Furthermore, in the compressed mode, when the TPC bits are 10B, atransmission power control amount of +1.0 dB (decibel) is applied, andwhen the TPC bits are 01B, a transmission power control amount of −1.0dB is applied. That is, when the TPC bits are at 10B or 01B, the unit oftransmission power control in the compressed mode is 1 dB.

Thus, the transmission power control unit is varied in the compressedmode in order to improve the adhesion capability of the transmissionpower control, making it possible to appropriately accommodate changesin the idle period (non-transmission timing) in the compressed mode.

Next, the operation will be explained. The eighth embodiment differsfrom the other embodiments in respect of its transmission power controlfunction, and therefore only the transmission power control will beexplained. FIG. 31 is a flowchart explaining the transmission powercontrol operation in compressed mode according to the eighth embodiment.Transmission power control of the transmitter 1D and the receiver 2Dexplained here is the transmission power control to an uplink.

A TPC bit from the receiver 2D and reception power information on thereceiver 2D side are sent to the transmitter 1D. When the transmitter 1Dreceives the TPC bit and the reception power information (Step S801) itdetermines the value of the TPC bits (Step S802). Then, the table ofFIG. 30 is consulted, and a desired transmission power increase/decreaseinformation is set, based on the determination in the Step S802 (StepS803). Then, transmission to the radio frequency transmitter 15 iscontrolled at the set transmission power (Step S804).

More specifically, for instance, when the TPC bits are 11B, aninstruction is made to increase the transmission power, and thetransmission power control of +3 dB from the above-mentioned table ofFIG. 30 is set. Therefore, an instruction to transmit after raising thepresent transmission power by 3 dB is sent to the radio frequencytransmitter 15. On the other hand, when the TPC bits are 00B, aninstruction is given to decrease the transmission power, by setting thetransmission power control of −3 dB from the table of theabove-mentioned FIG. 30. Therefore, an instruction to transmit afterdecreasing the present transmission power by 3 dB is sent to the radiofrequency transmitter 15.

Furthermore, when the TPC bits are 10B, an instruction is made toincrease the transmission power, and the transmission power control of+1 dB from the above-mentioned table of FIG. 30 is set. Therefore, aninstruction to transmit after raising the present transmission power by1 dB is sent to the radio frequency transmitter 15. On the other hand,when the TPC bits are 01B, an instruction is given to decrease thetransmission power, by setting the transmission power control of −1 dBfrom the table of the above-mentioned FIG. 30. Therefore, an instructionto transmit after decreasing the present transmission power by 1 dB issent to the radio frequency transmitter 15.

As described above, according to the eighth embodiment, transmissionpower is controlled in compliance with transmission power control unitsin correspondence with the normal mode and the compressed mode, and inaddition, in correspondence with the temporal intervals of thetransmission power control in the compressed mode. Therefore, in thecompressed mode, even when the temporal intervals of the transmissionpower control fluctuate and become long during intermittenttransmission, it is possible to use an appropriate transmission powercontrol range, and thereby maintain adhesion to the transmission power.As a consequence, the amount of error of transmission power control inthe compressed mode can be reduced.

The number of TPC bits and the transmission power is greater than theseventh embodiment described above. However, transmission power is inany case greater in compressed mode so that the needed transmissionpower of the TPC bit is attained by that greater power. Consequently,there is a merit that the transmission error rate has almost no effecton the control performance.

Furthermore, in the eighth embodiment, in the compressed mode, acompressed frame may be slotted and transmitted intermittently in N slotunits in the same manner as in the third embodiment described above.Consequently, it is possible to receive transmission power control bitstransmitted in the downlink in comparatively short time intervals. As aresult, the amount of error in the transmission power control can bereduced.

In the embodiments 1 to 8 explained above, the transmission format inthe compressed mode has a constitution for maintaining interleavingperformance and transmission power control precision, but the presentinvention is not restricted to this, and it is acceptable to set thetransmission format in consideration of reducing the number of spreadingcodes used, as in the following ninth embodiment.

Firstly, the constitution of a base station in which the CDMA system ofa ninth embodiment of the present invention has been applied will beexplained. The constitution of the mobile stations will be not explainedhere. FIG. 32 is a block diagram showing an example constitution of abase station according to the ninth embodiment of the present invention.As shown in FIG. 32, this base station comprises a transmitter group100, an adder 110, a radio frequency transmitter 120, a compressed modecontroller 200 which is connected to the transmitter group 100 andcontrols transmission in the compressed mode, etc. Radio communicationbetween the base station and mobile stations not shown in the diagramare performed using the CDMA communication method.

The transmitter group 100 comprises multiple transmitters #1 to #M(where M is a natural number) for creating transmission data separatelyfor users in correspondence with a serviceable number of users. Each ofthe transmitters #1 to #M has the same constitution. The constitutionwill be explained taking the transmitter #1 as an example. As shown inFIG. 32, the transmitter #1 comprises a controller 11E, theerror-correction encoder 12, the interleaver 13, a framing/spreadingunit 14E, a transmission power control amplifier 16, etc.

Through negotiations with the compressed mode controller 200, thecontroller 11E mainly controls the operations of the interleaver 13, theframing/spreading unit 14E, and the transmission power control amplifier16. In the compressed mode, the controller 11E supplies transmissiontimings for transmitting compressed mode frames, and spreading codeshaving a lower spreading factor than those normally used fortransmitting compressed mode frames, to the framing/spreading unit 14E.

The error-correction encoder 12 and the interleaver 13 are the same asin the first embodiment already described above, and explanation thereofwill be omitted. As regards the interleaver 13, it has a memory forinterleaving one frame.

The framing/spreading unit 14E spreads the band using spreading codes ofdifferent spreading factors in correspondence with the normal mode andthe compressed mode, and forms a frame for each mode. When thecontroller 11E has instructed transmission timings in correspondencewith each of the modes, the framing/spreading unit 14E sends the framesto the transmission power control amplifier 16 in accordance with thetransmission timing. Furthermore, in the compressed mode, thisframing/spreading unit 14E receives an instruction from the controller11E to lower the spreading factor, and in accordance with thatinstruction it obtains a transmission signal using a lower spreadingfactor than in the normal mode.

In compliance with the control of the controller 11E, the transmissionpower control amplifier 16 amplifies the average transmission power ofthe transmission signal, obtained by the framing/spreading unit 14E, inthe compressed mode as compared with the normal mode, and outputs thetransmission signal. The transmitters #1 to #M independently determinewhether or not to use compressed mode transmission, and furthermore,since the ratio of compression in the compressed mode is setindependently by the individual transmitters #1 to #M, transmissionpower control amplifiers 16 are provided independently to the individualtransmitters #1 to #M.

The adder 110 adds the transmission signals outputted from thetransmitters #1 to #M comprising the transmitter group 100, and sendsthem to the radio frequency transmitter 120 provided in thelatter-stage. The radio frequency transmitter 120 converts the signaloutput obtained by the adder 110 to a radio frequency, and transmits it.One radio frequency transmitter 120 is provided in each base station.

As shown in FIG. 32, the compressed mode controller 200 comprises acompressed mode manager 201, a frame combination controller 202, aspreading code allocation controller 203, a transmission timingcontroller 204, etc. The compressed mode manager 201 manages thecompressed mode of each transmitter in the transmitter group 100, andinputs/outputs control data for to the compressed mode.

The frame combination controller 202 receives transmission periodinformation about compressed mode frames of transmitters performingcompressed mode transmission from the compressed mode manager 201. Incompliance with that transmission period information, the framecombination controller 202 searches among the multiple compressed modeframes for a combination of frames having a total transmission timingwhich is within one frame duration.

The spreading code allocation controller 203 allocates a spreading code,to be used for spreading a compressed mode frame, to transmitterstransmitting in the compressed mode. The transmission timing controller204 controls the timings at which compressed mode frames are to betransmitted in the compressed mode.

Next, frame transmission including compressed mode will be explained.FIG. 33 is a diagram explaining frame transmission of a downlinkaccording to the ninth embodiment. In FIG. 33, the vertical axisrepresents transmission rate/transmission power, and the horizontal axisrepresents time. In the CDMA system, during normal transmission, aperiod of time is provided to slot the frame and transmit itintermittently, and the strength of the other frequency carriers ismeasured using the fact that the frames are not transmitted (idleperiod) during that period.

For that purpose, the slotted frame must be compressed, and in aconventional method, the spreading factor is decreased when transmittingthe compressed frame. In this case, a smaller number of spreading codeshaving a lower spreading factor must be allocated to each user carryingout compressed mode transmission, consuming valuable spreading coderesources.

Accordingly, as shown in FIG. 33, for instance during compressed modetransmission between the base station of FIG. 32 and mobile stations M1and M2, a group of compressed mode frames is collected from among thecompressed mode frames created by multiple users in such a way that thecollected group has a total transmission period of less than one frameduration. The same spreading code having a low spreading factor isallocated to each frame in the group, and they are transmitted at timeswhich do not overlap within one frame duration, thereby enablingmultiple mobile stations to share one spreading code. That is, in thedownlink for the mobile stations M1 and M2, different spreading codes Aand B are fixedly allocated to the mobile stations M1 and M2 during thenormal mode (normal transmission).

On the contrary, in the compressed mode (slotted transmission), anidentical spreading code C is allocated to both of the mobile stationsM1 and M2, and the compressed mode frame transmission timings of themobile stations M1 and M2 are controlled so that their transmissiontimings which both use the spreading code C do not overlap, enabling thecompressed mode frame of each to be transmitted during the idle periodT2 or T1 of the other.

Next, the operation will be explained. Firstly, the operation of theframing/spreading unit 14E during the compressed mode in thetransmitters #1 to #M will be explained. FIG. 34 is a flowchartexplaining the transmission operation in the compressed mode accordingto the ninth embodiment of the present invention. The execution of theoperation of FIG. 34 is controlled by the controller 11E although theindividual operations are performed by various sections. In thecompressed mode, interleaving in one frame is instructed to theinterleaver 13 (Step S901), and the interleaver 13 interleaves oneframe. Then, information relating to the compressed mode frame is outputto the compressed mode controller 200 (Step S902).

Then, a negotiation is carried out with the compressed mode controller200, and a spreading factor (spreading code) instruction of thecompressed mode controller 200 and a compressed mode frame transmissiontiming are supplied to the framing/spreading unit 14E (Step S903).Moreover, the transmission power control amplifier 16 is instructed toincrease the average transmission power (Step S904), and the compressedmode frame is transmitted at a high transmission power. In this way,frames are transmitted intermittently (non-continuously) in thecompressed mode.

Next, the control operation in compressed mode of the compressed modecontroller 200 will be explained. FIG. 35 is a flowchart explaining thecompressed mode control operation according to the ninth embodiment. Theoperation of FIG. 35 is controlled by the compressed mode manager 201although the individual operations are performed by various sections inthe compressed mode controller 200. In FIG. 35, information relating tocompressed mode is gathered through communication between thetransmitters #1 to #M.

Accordingly, the channels are checked to determine whether they are inthe compressed mode (Step S911). Then, when it has been confirmed thatthere are multiple channels in the compressed mode (Step S912), thetransmission period of the compressed mode frame in each channel incompressed mode is checked (Step S913). On the other hand, if there areno multiple channels in the compressed mode in the Step S912, theprocessing returns to the Step S911.

When checking the transmission period in the Step S913, the transmissionperiods of the compressed mode frames extracted from each channel in thecompressed mode are calculated together in a given combination to formone transmission duration. Then, it is determined whether the totaltimes of the combinations include any combinations which can fit intoone frame duration (Step S914).

As a result, when there is a combination which can fit into one frameduration, that combination is used for compressed mode frametransmission by allocating a single spreading code and mutuallydiffering transmission timings to the channels (transmitters) of thecompressed mode frames included in the combination (Step S915). On theother hand, if there are no combinations which can fit into one frameduration, multiple channels cannot be transmitted with a singlespreading code, and so the processing returns to the Step S911.

As described above, according to the ninth embodiment, in the compressedmode controller 200, a combination is extracted from given combinationsof multiple compressed mode frames compressed by separate users in thetransmitter group 100, the extracted combination having a totaltransmission timing of less than one frame duration, the same spreadingcode is allocated to each of multiple channels which transmit theextracted combination, and the transmission timings of the compressedmode frames which comprise the above extracted combinations arecontrolled in such a manner that they do not temporally overlap withinone frame duration, while using the same spreading code. As aconsequence, when there are multiple compressed mode frames, it ispossible to reduce the number of spreading codes having low spreadingfactors used in the compressed mode. As a result, spreading coderesources can be effectively used in the compressed mode.

Furthermore, in the ninth embodiment, in the compressed mode, acompressed frame may be divided into the front and rear of the sameframe timing as in the normal mode, and transmitted intermittently incompliance with that arrangement in the same manner as in the secondembodiment described above. Consequently, it is possible to secure anappropriate interleaving time in compressed mode in the same way as inthe normal mode, with a simple interleave constitution. As a result,poor performance caused by interleaving in bit units can be prevented.

Furthermore, in the ninth embodiment, in the compressed mode, acompressed frame may be slotted and transmitted intermittently in N slotunits in the same manner as in the third embodiment described above.Consequently, it is possible to receive transmission power control bitstransmitted in the downlink in comparatively short time intervals. As aresult, the amount of error in the transmission power control can bereduced.

In the above explanation, only a sample of an example combination of thecharacteristic parts of the embodiments 1 to 9 was shown, and othercombinations thereof can of course be realized.

The embodiments 1 to 9 of the present invention were explained above,but various modifications are possible within the range of the mainpoints of the present invention, and these are not excluded from therange of the invention.

The embodiments 1 to 9 described above explain how a period of time isprovided to slot the frame and transmit it intermittently, and thestrength of other frequency carriers is measured using non-transmissiontime, i.e. idle period, during that period. However, the method ofestablishing synchronization between the mobile stations and the basestation in an actual handover between different frequencies was notmentioned. Therefore, a communication device capable of realizinghandovers between different frequencies using the invention, and amethod of establishing synchronization thereof, will be explained below.

Firstly, before describing a handover between different frequencies, theconstitution of information transmitted and received between the mobilestations and the base station will be explained.

FIG. 37 shows a frame constitution of a broadcast channel (BCH). In aW-CDMA system, as shown in FIG. 37 (a), one frame of the broadcastchannel comprises sixteen slots, for instance, corresponding to #1 to#16 in the diagram. Furthermore, as shown in FIG. 37 (b), one slotcomprises ten symbols (representing one cycle of the spreading code). Inthis constitution, the four symbols shown by “P” in the diagram arepilot symbols needed for detecting phase information, the five symbolsshown by “D1 to D5” in the diagram are information components of thebroadcast channel, and one symbol shown by “FSC” (first search code) and“SSC” (second search code) in the diagram is a search code. The firstsearch code and the second search code are transmitted at the same time.

Furthermore, in the W-CDMA system, spectrum spreading is performed usingspreading codes, the spreading codes comprising two elements called aspreading code (short code) specific to the channels, and a scramblingcode (long code) specific to the base stations (see FIG. 37(c) and FIG.37(d)). The same spreading code is used for the pilot symbol P and theinformation components D1 to D5, and different spreading codes (COMMONand C+Walsh in the diagram) are used for the search codes. Furthermore,only the search code is not spread by the scrambling code. Next, thenormal mode sequence of establishing synchronization between the basestation and the mobile stations in the W-CDMA system will be explainedkeeping in mind the basic assumption (constitution of the broadcastchannel frame) mentioned above.

In a W-CDMA system, the cells are basically unsynchronized, that is, theframe timings and the like do not generally match. Accordingly, in theW-CDMA system, the mobile stations and the base stations can besynchronized using, for instance, a three-stage initial acquisitionmethod.

In the first stage, a first search code (FSC), being transmittedcommonly from all the base stations and time-continually, is detected.Using this, slot synchronization can be established.

In the second stage, multiple second search codes (SSC), transmitted atthe same timing as the first search code, are detected continuously insixteen slots, and determined in their transmission sequence. As aconsequence, frame synchronization can be established, and moreover, ascrambling code group number can be identified. More specifically, forinstance, as shown in FIG. 38, the second search codes are detected insixteen continuous slots. Then, frame synchronization can beaccomplished from one cycle comprising #1 to #16 from the second searchcodes detected in this manner. Moreover, the scrambling code groupnumber can be identified based for instance on a correspondence tablesuch as that shown in FIG. 39. Here, the slot # on the horizontal axisrepresent slot numbers, and the groups on the vertical axis representscrambling code groups. Furthermore, there are seventeen types of secondsearch codes (1 to 17), and from a combination of sixteen slots it ispossible to uniformly identify the scrambling code group number, i.e.the scrambling code used by the base station which the mobile stationbelongs to. The numeric values of the second search codes stored in thistable are one specific example to explain the present invention, and inthe sense of identifying a given numeric pattern, other numeric valuescan of course be used.

In the third stage, it is identified which of the multiple scramblingcodes contained in the scrambling group numbers are being used, tocomplete the establishment of synchronization of the downstream line ofthe corresponding base station.

FIG. 40 is a flowchart of a case when the synchronization establishmentsequence described above is actually being performed on the mobilestation side. Below, the operation of the mobile station will beexplained based on FIG. 37.

Firstly, the mobile station performs processing corresponding to thefirst stage, by detecting the first search code (Step S921). Detectionis carried out continuously until a first search code is detected (StepS922).

When the first search code has been detected (YES in the Step S922), themobile station synchronizes the slots, and then detects sixteen secondsearch codes in the second stage (Step S923). Here, at the mobilestation, when a second search code cannot be detected due to thecondition of the channels or the like (NO in Step 924), the number ofundetected places is counted (Step S925), and it is determined whetherthere are more or less of these than a predetermined number set inadvance (Step S926). For instance, when there are more of them, thesecond search code is detected again (Step S923), and on the other hand,when there are fewer of them, only that portion is detected (Step S927and Step 928).

In this way, when all the second search codes have been detected (YES inthe Step S924, and YES in the Step 928), as explained above, the mobilestation establishes frame synchronization, and identifies the scramblingcode group number.

Finally, as the third stage, the mobile station identifies thescrambling code used by the corresponding base station (Step 931, YES inStep 932), completing the establishment of initial synchronization. Thuscommunication becomes possible. When calculating the correlation valueof the identified scrambling codes (Step S933), when all the codes arebelow a predetermined reference value (YES in Step 934), the secondsearch codes are detected again (Step S923); otherwise (NO in the StepS934), the scrambling codes are reidentified until the Step 931 iscompleted.

On the other hand, as explained earlier (in a case requiring a handoveras explained in the conventional technology), when performing a handoverbetween different frequencies, the power of other carriers is measuredin compliance with an order from the base station or a determinationcarried out by the mobile station, and if there is a carrier which seemsactually capable of a frequency handover, the handover is carried outaccording to a predetermined sequence. At that point, a first searchcode can be detected without fail, i.e., at least once in the idleperiod described in the above embodiments 1 to 9. However, to detect asecond search code it is necessary to search one frame, i.e. all sixteenslots, and consequently it cannot be detected in this way. Therefore,similarly, it is not possible to detect the scrambling code groupnumber.

Accordingly, it is an object of the present embodiment to realize acommunication device capable of detecting all second search codes bygradually shifting the idle period of not more than half of one frame.

FIG. 41 shows a constitution of a receiver according to a tenthembodiment of the present invention. This constitution is provided tothe mobile stations.

As shown in FIG. 41, the receiver 2E comprises a controller 21E, anerror-correction decoder 22, a deinterleaver 23, adeframing/de-spreading unit 24E, a radio frequency transmitter 25, atime/de-spreading unit 51, a detecting/determining unit 52, and a switch53. Parts of the constitution which are the same as the embodimentsalready described are represented by the same reference codes andexplanation thereof will be omitted.

Through negotiations with a transmitter not shown in the diagram, thecontroller 21E mainly controls the operations of the deinterleaver 23,the deframing/de-spreading unit 24E, and the switch 53. By negotiatingwith the transmitter, this controller 21E indicates frame numbers of theframes to be deinterleaved, appropriate to the normal mode and thecompressed mode. Furthermore, in the compressed mode, this controller21E supplies an instruction to reduce the spreading factor, andreception timings for receiving compressed mode frames, to the switch53, the deframing/de-spreading unit 2E, and the time/de-spreading unit51. That is, the switch 53 and the time/de-spreading unit 51 areconnected only in the idle period.

The radio frequency receiver 25 decodes received signals sent from anantenna not shown in the diagram. The deframing/de-spreading unit 24Ede-spreads using spreading codes allocated to the users of the receiver2E in correspondence with the normal mode and the compressed mode, andforms a frame for each mode. When the controller 21E has instructed thedeframing/de-spreading unit 24E of reception timings in correspondencewith each of the modes, the deframing/de-spreading unit 24E extracts thereceived signals from the radio frequency receiver 25 in accordance withthe reception timings. Furthermore, in the compressed mode, thedeframing/de-spreading unit 24E receives an instruction from thecontroller 21E to reduce the spreading factor, and, in accordance withthat instruction, obtains a received signal using a lower spreadingfactor than in the normal mode. The deinterleaver 23 chronologicallyinterleaves (deinterleaves) the coded data in bit units, in a reversesequence to the interleaving in the transmitter. The error-correctiondecoder 22 corrects errors in the deinterleaved signal to obtain decodeddata, i.e. a received data stream.

Furthermore, during the idle period, the time/de-spreading unit 51detects first search codes and second search codes on other carriers.The detecting/determining unit 52 carries out a determining process,described later, based on the detected first search codes and secondsearch codes.

The receiver 2E having the constitution as shown in FIG. 42 normallyreceives a compressed frame on a carrier (frequency: f1) being used incommunication. In idle period this receiver 2E receives the search codeon another carrier (frequency: f2).

Next, the operation in the receiver 2E when performing a handover willbe explained. FIG. 43 is a flowchart of the procedures of establishingsynchronization performed on the mobile station side during a handoverbetween W-CDMA/W-CDMA different frequencies. In the handover explainedbelow, the controller 21E carries out control based on a determinationof the detecting/determining unit 52.

For instance, in the case of a handover performed in accordance with acommand from the base station or a determination of the mobile station,the mobile station extracts cell information of other frequency carriersfrom the base station (Step S941).

Next, based on the extracted information, the mobile station carries outprocessing corresponding to the first stage by detecting a first searchcode and a different frequency carrier during the idle period of thecompressed mode (Step S942). Basically, this detecting is performedcontinuously until the first search code is detected (Step S943), butreturns to redetecting the cell information and the first search code inaccordance with a setting of the receiver (Step S944). During the idleperiod, the switch 53 is connected to the timing/de-spreading unit 51 incompliance with the controller 21E.

When the first search code and the different frequency carrier have beendetected (YES in the Step S943), the mobile station establishes slotsynchronization, and then detects sixteen second search codes in thesecond stage (Step S945). As the second search code detection, as forinstance shown in FIG. 44, the controller 21E shifts the idle period foreach slot, and detects one second search code in each frame. That is,all the second search codes are detected in sixteen frames.

Furthermore, the method of detecting the second search code is notrestricted to this, and two second search codes may be detected in oneframe, as for instance shown in FIG. 45. This case differs form FIG. 44in that all the second search codes can be detected in eight frames.Furthermore, when continuously controlling multiple frames (two framesare shown in the diagram), as for instance shown in FIG. 46 and FIG. 47,all the second search codes can be detected by setting the idle period.As explained above, the idle period needs only to be set to a maximum ofhalf the duration of one frame, there being many conceivable variationsother than the above. Therefore, the number of frames detected variesaccording to the length of the idle period. Furthermore, detectionreliability can be improved by detecting all the second search codes anumber of times.

However, when the idle period is set long, although the detection timedoes not take longer than when the idle period is short, there may besome deterioration in the quality of information data that was beingtransmitted, or interference power may be increased if the transmissionpower is increased to maintain the quality of this data. On the otherhand, when the idle period is shortened, although there is not as muchdeterioration in the quality of information data as compared to when theidle period is long, the detection time is much longer. Accordingly, anoptimum idle period must be set at the receiver side, with considerationto synthesizer performance (synthesizer switching time and the like) andthe channel condition and the like. Furthermore, the portions in theframes of FIG. 45 to FIG. 47 where the slots overlap must be set asappropriate in accordance with synthesizer performance (synthesizerswitching time and the like).

In the Step S945, when the mobile station is unable to detect a secondsearch code due to the condition of the channel (NO in Step S924), thenumber of undetected places is counted (Step S925), and it is determinedwhether there are more or fewer than a predetermined number (Step S926);for instance, when there are more, the second search codes are detectedagain, on the other hand, when there are fewer, detecting is carried outin that portion only.

In this way, when all the second search codes have been detected (YES inthe Step S924, or YES in the Step 928), the mobile station establishesframe synchronization to the other carrier, and identifies thescrambling code group number of the corresponding base station.

Finally, as the third stage, the mobile station identifies thescrambling code used by the corresponding base station (Step 931, YES inStep 932), completing the establishment of initial synchronization inthe handover. Thus communication is possible. When calculating thecorrelation value of the identified scrambling codes (Step S933), whenall the codes are below a predetermined reference value (YES in Step934), the second search codes are detected again (Step S923); otherwise(NO in the Step S934), the scrambling codes are reidentified until theStep 931 is completed.

Next, a handover operation with another communication system known asGSM (Global System for Mobile Communication) will be explained using thediagrams. This handover is also performed at the receiver 2E shown inFIG. 41. Therefore, in this case, instead of the first search codes andthe second search codes, the time/de-spreader 51 detects FCCH and SCHexplained below.

FIG. 48 is a diagram showing a constitution of a GSM superframe. FIG. 48(a) is a GSM control channel, that is, a channel showing controlinformation such as a Frequency Correction CH (FCCH) for tuningfrequencies, a Synchronization CH (SCH) for synchronizing, as well asother information. FIG. 48 (b) shows a GSM Traffic CH (TCH).Furthermore, FIG. 49 is a flowchart in a case when a mobile stationestablishes synchronization in a handover between W-CDMA and GSM.

Firstly, as a first stage, the W-CDMA mobile station must discover wherethe GSM frequency carrier is, and so repeatedly coarsely measures poweruntil it finds the carrier (Step S951 and Step S952).

Next, when the mobile station has finished power measurement, as asecond stage, based on the measurement result, it finely adjusts thecarrier frequency, measured by capturing the FCCH, and identifies theGSM carrier (Step S953). In the GSM, one superframe comprises fifty-oneframes, including five FCCH. Therefore, the W-CDMA system mobile stationtunes the frequency in these five periods (Step S954 and Step S955).Furthermore, the FCCH can be detected without shifting the idle period,by utilizing the fixed time difference between the FCCH/SCH superframesynchronization and the superframe synchronization in the W-CDMA system.However, the FCCH can be detected by gradually shifting the idle period,in the same way as in the above-mentioned handover between W-CDMAsystems.

Finally, when the GSM carrier has been identified, as a third stage, themobile station capture the SCH, which is the frame next to the FCCH, andsynchronizes the bit timings (Step S956, Step S957, and Step S958). Forinstance, if the detection of the FCCH is complete, the position of theSCH is already known (it is the next frame) and thus it can easily bedetected. Therefore, although it is necessary to identify all thesuperframes to detect the FCCH, the SCH can be detected merely bysetting the idle period so that the frame next to the FCCH can bedetected. However, when detecting the SCH, there is no need to capturethe SCH immediately after the captured FCCH; for instance, the SCHimmediately after the next FCCH can be captured, or any SCH can becaptured. As a consequence, the W-CDMA system mobile station completesthe establishment of initial synchronization in the handover, enablingcommunication with the GSM to be carried out.

In this way, according to the present embodiment, a handover can easilybe achieved between different frequencies (between a W-CDMA system and aW-CDMA system, and between a W-CDMA system and a GSM).

The above embodiments 1 to 10 describes in detail the spread spectrumcommunication device of the present invention, and the operations ofthese embodiments share the process of using an interleaver tochronologically interleave in bit units coded data, and thereafter,using a framing/spreading unit to compress the interleaved data.However, the interleaving of data does not necessarily have to beperformed prior to compression, and can basically be performed in anypoint. For instance, the interleaving may be performed after the datahas been compressed. Therefore, when interleaving after the data hasbeen compressed, the error-correction encoder has the function ofcompressing the data, and there is no need for provide aframing/spreading unit. In such a case, the constitution of the receiverside naturally changes. That is, the deinterleave processing isperformed first.

INDUSTRIAL APPLICABILITY

As above, the spread spectrum communication device according to thepresent invention is useful for a code division multiple access (CDMA)communication system, and is especially applicable to spread spectrumcommunication carrying out interleaving transmission and transmissionpower control, and moreover, is applicable as a communication device forcarrying out a handover between different frequencies (between a W-CDMAsystem and a W-CDMA system, and between a W-CDMA system and a GSM).

1. A code division multiple access system continuously transmittinguncompressed frames in a normal mode; and intermittently transmittingcompressed frames in a compressed mode, comprising, a base station,including a transmitting unit (15) that transmits transmission powercontrol information to a mobile station, the power control informationinstructing indicating an increase or a decrease in transmission power;and the mobile station, including a receiving unit (25) configured toreceive transmission power control information indicating an increase ora decrease in power from a base station, a compressing unit (14)configured to compress a frame so as to produce a compressed frame incompressed mode, an interleaving unit (13) configured to performinterleaving in bit units on an uncompressed frame in normal mode and onthe compressed frame in compressed mode, a transmitting unit (15)configured to transmit frames and a control unit (11) configured tocontrol said compressing unit (14), said interleaving unit (13) and saidtransmitting unit (15); characterized in that said compressing unit(14), said interleaving unit (13) and said transmitting unit (15) areconfigured to be controlled so as to divide the compressed frame into afront portion of a frame window and a rear portion separated from thefront portion, where said front portion has a front edge of a framewindow and said rear portion has a rear edge of said frame window, andadjust transmission power on the uncompressed frames in normal mode andcompressed frames in compressed mode in accordance with the transmissionpower control information, by increasing or decreasing currenttransmission power with one of a (first) plurality of power control stepsizes for the normal mode and one of a (second) plurality of powercontrol step sizes for the compressed mode.
 2. A code division multipleaccess system continuously transmitting uncompressed frames in a normalmode; and intermittently transmitting compressed frames in a compressedmode, comprising, a mobile station, including a transmitting unit (15)that transmits transmission power control information to a base station,the power control information instructing indicating an increase or adecrease in transmission power; and the base station, including areceiving unit (25) configured to receive transmission power controlinformation indicating an increase or a decrease in power from a mobilestation, a compressing unit (14) configured to compress a frame so as toproduce a compressed frame in compressed mode, an interleaving unit (13)configured to perform interleaving in bit units on an uncompressed framein normal mode and on the compressed frame in compressed mode, atransmitting unit (15) configured to transmit frames and a control unit(11) configured to control said compressing unit (14), said interleavingunit (13) and said transmitting unit (15); characterized in that saidcompressing unit (14), said interleaving unit (13) and said transmittingunit (15) are configured to be controlled so as to divide the compressedframe into a front portion of a frame window and a rear portionseparated from the front portion, where said front portion has a frontedge of a frame window and said rear portion has a rear edge of saidframe window, and adjust transmission power on the uncompressed framesin normal mode and compressed frames in compressed mode in accordancewith the transmission power control information, by increasing ordecreasing current transmission power with one of a (first) plurality ofpower control step sizes for the normal mode and one of a (second)plurality of power control step sizes for the compressed mode.
 3. A basestation in a code division multiple access system continuouslytransmitting uncompressed frames in a normal mode; and intermittentlytransmitting compressed frames in a compressed mode, comprising, areceiving unit (25) configured to receive transmission power controlinformation indicating an increase or a decrease in power from a mobilestation, a compressing unit (14) configured to compress a frame so as toproduce a compressed frame in compressed mode, an interleaving unit (13)configured to perform interleaving in bit units on an uncompressed framein normal mode and on the compressed frame in compressed mode, atransmitting unit (15) configured to transmit frames and a control unit(11) configured to control said compressing unit (14), said interleavingunit (13) and said transmitting unit (15); characterized in that saidcompressing unit (14), said interleaving unit (13) and said transmittingunit (15) are configured to be controlled so as to divide the compressedframe into a front portion of a frame window and a rear portionseparated from the front portion, where said front portion has a frontedge of a frame window and said rear portion has a rear edge of saidframe window, and adjust transmission power on the uncompressed framesin normal mode and compressed frames in compressed mode in accordancewith the transmission power control information, by increasing ordecreasing current transmission power with one of a (first) plurality ofpower control step sizes for the normal mode and one of a (second)plurality of power control step sizes for the compressed mode.
 4. Amobile station in a code division multiple access system continuouslytransmitting uncompressed frames in a normal mode; and intermittentlytransmitting compressed frames in a compressed mode, comprising, areceiving unit (25) configured to receive transmission power controlinformation indicating an increase or a decrease in power from a basestation, a compressing unit (14) configured to compress a frame so as toproduce a compressed frame in compressed mode, an interleaving unit (13)configured to perform interleaving in bit units on an uncompressed framein normal mode and on the compressed frame in compressed mode, atransmitting unit (15) configured to transmit frames and a control unit(11) configured to control said compressing unit (14), said interleavingunit (13) and said transmitting unit (15); characterized in that saidcompressing unit (14), said interleaving unit (13) and said transmittingunit (15) are configured to be controlled so as to divide the compressedframe into a front portion of a frame window and a rear portionseparated from the front portion, where said front portion has a frontedge of a frame window and said rear portion has a rear edge of saidframe window, and adjust transmission power on the uncompressed framesin normal mode and compressed frames in compressed mode in accordancewith the transmission power control information, by increasing ordecreasing current transmission power with one of a (first) plurality ofpower control step sizes for the normal mode and one of a (second)plurality of power control step sizes for the compressed mode.